Repository: nervosnetwork/ckb (language: rust)

Issue:
Support Replace-by-fee in memory pool
## Feature Request

#### Is your feature request related to a problem? Please describe.
CKB only supports Child-pay-for-parent fee-bumping mechanism, but CPFP is not available in some scenarios. For example, when all the cell outputs have a since precondition.

#### Describe the solution you'd like
Add opt-in mechanism to replace a transaction in the memory pool.

- The user must set a flag to show that a transaction can be replaced.
- The new transaction must have a higher fee weight and a total fee amount.

#### References

- https://bitcoincore.org/en/faq/optin_rbf/



Discussion / hints:
@code-monad has proposed a solution. We'll hold for now and will push forward when this issue gets enough discussions.

@code-monad could you post your proposal public?
# RBF in CKB(draft 2023.01.05)

old one: 

[RBF in CKB(deprated)](https://www.notion.so/RBF-in-CKB-deprated-30d536c4d8f14ea2987039c4cdf4607d)

Refers:

[Opt-in RBF FAQ](https://bitcoincore.org/en/faq/optin_rbf/)

[https://github.com/bitcoin/bitcoin/pull/6871/files#diff-34d21af3c614ea3cee120df276c9c4ae95053830d7f1d3deaf009a4625409ad2](https://github.com/bitcoin/bitcoin/pull/6871/files#diff-34d21af3c614ea3cee120df276c9c4ae95053830d7f1d3deaf009a4625409ad2)

### Side Notes:

`txid` in CKB will change hence the `fee` and weight was changed. a simple inject-replace is impossible.

# Analysis

*The key point is*, submmit the new tx **before** old one. Since `ChunkQueue` is **FIFO**, so the simplest way is insert new tx into its head.

### other details

A tx replacement must follow

1. The transaction is submitted through new extended version of `SubmitLocalTx` and `SubmitRemoteTx` called `SubmitLocalTxReplaceable` and `SubmitRemoteTxReplaceable`. In the client side which is send through RPC `send_transaction_replaceable` 
2. Assume that a Tx called “Tx_A” was submmited  with these functions/calls will be marked as `replaceable` in `TxPool`
3. Client can construct a new replace tx called “TX_B” with **any same `input`** before the original tx’s status becomes `Committed` or `Rejected`
4. The Tx_B **must** have a higher fee, and spends the **same** *input cell* with Tx_A
5. The Tx_B will be inserted into a high priority queue, chunk’s process will pop and use value inside it, until it’s empty, then `self.front`
6. When submitting tx from high priority queue, it will first check if the hash of it’s input is still in the map; If not, it means that this tx is no longer replaceable(whether `Committed` or `Rejected`), this tx will be ***rejected***(not accepted as a replacement)
7. When process a tx in tx_pool, it will first check if any input of this tx is found in the record map, if so, this is a replacement tx, which will perfoms a rbf; if not, it will continue the original resolve process

# Solution Design

So the modification would be:

## 1. Adding parameters to  `SubmitLocalTx` and `SubmitRemoteTx`

adds a `bool` in `ckb_tx_pool::service::Message`

```rust
pub(crate) enum Message {
//.....
		SubmitLocalTx(Request<TransactionView, bool, SubmitTxResult>),
    SubmitRemoteTx(Request<(TransactionView, bool, Cycle, PeerIndex), ()>),
//....
}
```

## 2. Adding new rpc

Adds `send_transaction_replaceable` , make `send_transaction` as a wrapper for it, defaults replaceable is `false`

```rust
#[rpc(name = "send_transaction_replaceable")]
    fn send_transaction_replaceable(
        &self,
        tx: Transaction,
	replaceable: bool,
        outputs_validator: Option<OutputsValidator>,
    ) -> Result<H256>;
```

## 3. Adding fields into `TxEntry`

```rust
/// An entry in the transaction pool.
#[derive(Debug, Clone, Eq)]
pub struct TxEntry {
    /// Transaction
    pub rtx: ResolvedTransaction,
    /// Cycles
    pub cycles: Cycle,
    /// tx size
    pub size: usize,
    /// fee
    pub fee: Capacity,
    //......
    pub timestamp: u64,
    **/// The flag to show whether this transaction can be replaced**
    **pub replaceable: bool,**
}
```

## 4. Adding new field to `TxPool`

Adds a map that records all inputs in a replaceable tx

```rust
/// Tx-pool implementation
pub struct TxPool {
    pub(crate) config: TxPoolConfig,
    /// The short id that has not been proposed
    pub(crate) pending: PendingQueue,
    /// The proposal gap
    pub(crate) gap: PendingQueue,
    /// Tx pool that finely for commit
    pub(crate) proposed: ProposedPool,
    /// cache for committed transactions hash
    pub(crate) committed_txs_hash_cache: LruCache<ProposalShortId, Byte32>,
    // sum of all tx_pool tx's virtual sizes.
    pub(crate) total_tx_size: usize,
    // sum of all tx_pool tx's cycles.
    pub(crate) total_tx_cycles: Cycle,
    /// storage snapshot reference
    pub(crate) snapshot: Arc<Snapshot>,
    /// record recent reject
    pub recent_reject: Option<RecentReject>,
    // expiration milliseconds,
    pub(crate) expiry: u64,

    // records the replaceable tx's inputs
    pub replaceable_inputs: HashMap<Outpoint, ProposalShortId>,
}
```

## 5. Check if a tx is replaceable brefore resolve

In `Precheck`,there’s a method call named `resolve_tx_from_pending_and_proposed`, which is used to check if a tx used a seen input in pool

```rust
pub(crate) fn resolve_tx_from_pending_and_proposed(
        &self,
        tx: TransactionView,
    ) -> Result<ResolvedTransaction, Reject> {
				//......
				//......
				// Check if tx's inputs is marked replaceable
				if **check_replaceable(tx) {
					// deal with replaceable inputs
					// maybe just act as a normal tx
				} else {
	        resolve_transaction(
            tx,
            &mut seen_inputs,
            &pending_and_proposed_provider,
            snapshot,
	        )
	        .map_err(Reject::Resolve)
				}

    }
```

All inputs which contain in the tx that the conflict replaceable input from should be removed from `TxPool.replaceable_inputs` 

## 6. Remove old tx if a tx is replaced by another tx

Since the replacement will never happen when after a tx being `Commited`/ `Rjected`,the original tx shall be able to remove from the pool.

## 7. What will happen if a replace tx submitted too late after the original tx Committed?

It will not become a new tx, because the replace tx spends the same input cell with the original one.

## 8. Adding replaceable mark into `RelayTransaction`

check:  [https://github.com/nervosnetwork/ckb/blob/develop/util/types/schemas/extensions.mol#L155](https://github.com/nervosnetwork/ckb/blob/develop/util/types/schemas/extensions.mol#L155)

```rust
table RelayTransaction {
    cycles:                     Uint64,
    transaction:                Transaction,
    replaceable:                BoolOpt,
}
```

## 9. Adding replaceable mark to `PoolTransactionEntry` in `util/types/src/core/service.rs`

```rust
// util/types/src/core/service.rs
/// Notify pool transaction entry
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct PoolTransactionEntry {
    /// Transaction view
    pub transaction: TransactionView,
    /// Transaction consumed cycles
    pub cycles: Cycle,
    /// Transaction serialized cycles
    pub size: usize,
    /// Transaction fee
    pub fee: Capacity,
    /// The unix timestamp when entering the Txpool, unit: Millisecond
    pub timestamp: u64,
    pub replaceable: bool,
}
```

This is used in `NotifyController::notify_new_transaction`

# Avoiding Spam and DDos

As a refer to [https://github.com/bitcoin/bitcoin/blob/master/doc/policy/packages.md#package-mempool-acceptance-rules](https://github.com/bitcoin/bitcoin/blob/master/doc/policy/packages.md#package-mempool-acceptance-rules)

We need to introduce some additional policy restriction to RBF feature:

1. The replacement tx can not contains any unconfirmed inputs in txpool. This can solve the “tx pin problem”
2. The replacement transaction should pay a higher effective fee rate than the total fee of the root of the set of transactions it replaces
3. The replacement transaction must also pay for replacing the original transactions at or above the rate set by the node's minimum fee. [https://github.com/nervosnetwork/ckb/wiki/Transaction-»-Transaction-Fee#min-transaction-fee-rate](https://github.com/nervosnetwork/ckb/wiki/Transaction-%C2%BB-Transaction-Fee#min-transaction-fee-rate)
4. Replace rate limitation: Assume that we set a time duration as a rate limit(for example 5s), if a tx was replaced within 5s before, then the incomming replace tx will be rejected directly

Fix patch:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1675622984..45cb473eaf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,16 @@
+### Features
+* #4079, **tx-pol:** Implement `Replace-by-Fee(RBF)` for tx-pool (@chenyukang)
+This feature enables users to replace a transaction with a higher fee rate, which is useful when the transaction is stuck in the tx-pool:
+    * Add `min_rbf_rate` in `ckb.toml` with default value `1500`, which means the minimum extra fee rate for RBF, the unit is `shannons/KB`
+    * Add fields `fee` and `min_replace_fee` in `get_transaction`, which means the the minimal fee need to pay for RBF for a specific transaction
+    * The replaced transaction will be removed from `tx-pool` and with the status `Rejected`.
+
+### Improvements
+* #3993, **tx-pool:** Almost reimplemented `tx-pool` with `multi_index_map`, with the following improvements (@chenyukang):
+  * Sort txs in pool by `score` in `Pending` stage, `txs` with higher `score` be processed first
+  * Evict `txs` from pool with `descendants_count` and `fee_rate`
+  * Eliminate redundant code for clean and consistent code
+
 # [v0.110.0](https://github.com/nervosnetwork/ckb/compare/v0.109.0...v0.110.0) (2023-05-15)
 
 ### Features
diff --git a/Cargo.lock b/Cargo.lock
index 8e42a97bf3..b83e58c5f8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1423,9 +1423,9 @@ dependencies = [
  "ckb-types",
  "ckb-util",
  "ckb-verification",
- "ckb_multi_index_map",
  "hyper",
  "lru",
+ "multi_index_map",
  "rand 0.8.5",
  "rustc-hash",
  "sentry",
@@ -1553,21 +1553,6 @@ dependencies = [
  "paste",
 ]
 
-[[package]]
-name = "ckb_multi_index_map"
-version = "0.0.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "53c20823dfd9f9a8e30faa3b0bdcab4801fb2544957586fada3884c78dcdf38b"
-dependencies = [
- "convert_case 0.6.0",
- "proc-macro-error",
- "proc-macro2",
- "quote",
- "rustc-hash",
- "slab",
- "syn",
-]
-
 [[package]]
 name = "clang-sys"
 version = "1.3.1"
@@ -3143,6 +3128,30 @@ dependencies = [
  "faster-hex",
 ]
 
+[[package]]
+name = "multi_index_map"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "03f409d5f41e6b8a2faa0b363c4523742f0ef5e4015fd4e298a5c7dbb3a3e01c"
+dependencies = [
+ "multi_index_map_derive",
+ "rustc-hash",
+ "slab",
+]
+
+[[package]]
+name = "multi_index_map_derive"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "98e81cd436463efbaa95a2d2bac3028e6998a4bb2ef8a82a661de3567bb79d5a"
+dependencies = [
+ "convert_case 0.6.0",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "native-tls"
 version = "0.2.11"
diff --git a/pow/src/lib.rs b/pow/src/lib.rs
index 4429f24b35..6ce8c1c163 100644
--- a/pow/src/lib.rs
+++ b/pow/src/lib.rs
@@ -27,10 +27,10 @@ pub enum Pow {
     /// Mocking dummy PoW engine
     Dummy,
     /// The Eaglesong PoW engine
-    /// Check details of Eaglesong from: https://github.com/nervosnetwork/rfcs/blob/master/rfcs/0010-eaglesong/0010-eaglesong.md
+    /// Check details of Eaglesong from: <https://github.com/nervosnetwork/rfcs/blob/master/rfcs/0010-eaglesong/0010-eaglesong.md>
     Eaglesong,
     /// The Eaglesong PoW engine, similar to `Eaglesong`, but using `blake2b` hash as the final output.
-    /// Check details of blake2b from: https://tools.ietf.org/html/rfc7693 and blake2b-rs from: https://github.com/nervosnetwork/blake2b-rs
+    /// Check details of blake2b from: <https://tools.ietf.org/html/rfc7693> and blake2b-rs from: <https://github.com/nervosnetwork/blake2b-rs>
     EaglesongBlake2b,
 }
 
diff --git a/resource/ckb.toml b/resource/ckb.toml
index 89ec89f6fb..9f99d4bb98 100644
--- a/resource/ckb.toml
+++ b/resource/ckb.toml
@@ -134,6 +134,8 @@ enable_deprecated_rpc = false # {{
 [tx_pool]
 max_tx_pool_size = 180_000_000 # 180mb
 min_fee_rate = 1_000 # Here fee_rate are calculated directly using size in units of shannons/KB
+# min_rbf_rate > min_fee_rate means RBF is enabled
+min_rbf_rate = 1_500 # Here fee_rate are calculated directly using size in units of shannons/KB
 max_tx_verify_cycles = 70_000_000
 max_ancestors_count = 25
 
diff --git a/rpc/README.md b/rpc/README.md
index 6db0bf3d40..0f1b0020fd 100644
--- a/rpc/README.md
+++ b/rpc/README.md
@@ -882,6 +882,8 @@ Response
     },
     "cycles": "0x219",
     "time_added_to_pool" : "0x187b3d137a1",
+    "fee": "0x16923f7dcf",
+    "min_replace_fee": "0x16923f7f6a",
     "tx_status": {
       "block_hash": null,
       "status": "pending",
@@ -4510,6 +4512,7 @@ Response
   "result": {
     "last_txs_updated_at": "0x0",
     "min_fee_rate": "0x3e8",
+    "min_rbf_rate": "0x5dc",
     "max_tx_pool_size": "0xaba9500",
     "orphan": "0x0",
     "pending": "0x1",
@@ -5072,6 +5075,10 @@ For example, a cellbase transaction is not allowed in `send_transaction` RPC.
 
 (-1110): The transaction exceeded maximum size limit.
 
+### Error `PoolRejectedRBF`
+
+(-1111): The transaction is rejected for RBF checking.
+
 ### Error `Indexer`
 
 (-1200): The indexer error.
@@ -6426,7 +6433,7 @@ TX reject message
 
 `PoolTransactionReject` is a JSON object with following fields.
 
-*   `type`: `"LowFeeRate" | "ExceededMaximumAncestorsCount" | "ExceededTransactionSizeLimit" | "Full" | "Duplicated" | "Malformed" | "DeclaredWrongCycles" | "Resolve" | "Verification" | "Expiry"` - Reject type.
+*   `type`: `"LowFeeRate" | "ExceededMaximumAncestorsCount" | "ExceededTransactionSizeLimit" | "Full" | "Duplicated" | "Malformed" | "DeclaredWrongCycles" | "Resolve" | "Verification" | "Expiry" | "RBFRejected"` - Reject type.
 *   `description`: `string` - Detailed description about why the transaction is rejected.
 
 Different reject types:
@@ -6441,6 +6448,7 @@ Different reject types:
 *   `Resolve`: Resolve failed
 *   `Verification`: Verification failed
 *   `Expiry`: Transaction expired
+*   `RBFRejected`: RBF rejected
 
 
 ### Type `ProposalShortId`
@@ -6949,6 +6957,10 @@ The JSON view of a transaction as well as its status.
 
 *   `tx_status`: [`TxStatus`](#type-txstatus) - The Transaction status.
 
+*   `fee`: [`Capacity`](#type-capacity) `|` `null` - The transaction fee of the transaction
+
+*   `min_replace_fee`: [`Capacity`](#type-capacity) `|` `null` - The minimal fee required to replace this transaction
+
 
 ### Type `TxPoolEntries`
 
@@ -7033,6 +7045,10 @@ Transaction pool information.
 
     The unit is Shannons per 1000 bytes transaction serialization size in the block.
 
+*   `min_rbf_rate`: [`Uint64`](#type-uint64) - RBF rate threshold. The pool reject to replace for transactions which fee rate is below this threshold. if min_rbf_rate > min_fee_rate then RBF is enabled on the node.
+
+    The unit is Shannons per 1000 bytes transaction serialization size in the block.
+
 *   `last_txs_updated_at`: [`Timestamp`](#type-timestamp) - Last updated time. This is the Unix timestamp in milliseconds.
 
 *   `tx_size_limit`: [`Uint64`](#type-uint64) - Limiting transactions to tx_size_limit
diff --git a/rpc/src/error.rs b/rpc/src/error.rs
index 1f86db9b72..e566e96eb2 100644
--- a/rpc/src/error.rs
+++ b/rpc/src/error.rs
@@ -112,6 +112,8 @@ pub enum RPCError {
     TransactionExpired = -1109,
     /// (-1110): The transaction exceeded maximum size limit.
     PoolRejectedTransactionBySizeLimit = -1110,
+    /// (-1111): The transaction is rejected for RBF checking.
+    PoolRejectedRBF = -1111,
     /// (-1200): The indexer error.
     Indexer = -1200,
 }
@@ -173,6 +175,7 @@ impl RPCError {
             Reject::DeclaredWrongCycles(..) => RPCError::PoolRejectedMalformedTransaction,
             Reject::Resolve(_) => RPCError::TransactionFailedToResolve,
             Reject::Verification(_) => RPCError::TransactionFailedToVerify,
+            Reject::RBFRejected(_) => RPCError::PoolRejectedRBF,
             Reject::ExceededTransactionSizeLimit(_, _) => {
                 RPCError::PoolRejectedTransactionBySizeLimit
             }
diff --git a/rpc/src/module/chain.rs b/rpc/src/module/chain.rs
index 08574e13bb..36e0f4238f 100644
--- a/rpc/src/module/chain.rs
+++ b/rpc/src/module/chain.rs
@@ -617,6 +617,8 @@ pub trait ChainRpc {
     ///     },
     ///     "cycles": "0x219",
     ///     "time_added_to_pool" : "0x187b3d137a1",
+    ///     "fee": "0x16923f7dcf",
+    ///     "min_replace_fee": "0x16923f7f6a",
     ///     "tx_status": {
     ///       "block_hash": null,
     ///       "status": "pending",
@@ -2130,11 +2132,11 @@ impl ChainRpcImpl {
                             .and_then(|v| v.get(tx_info.index.saturating_sub(1)).copied())
                     })
             };
-
             return Ok(TransactionWithStatus::with_committed(
                 None,
                 tx_info.block_hash.unpack(),
                 cycles,
+                None,
             ));
         }
 
@@ -2181,6 +2183,7 @@ impl ChainRpcImpl {
                 Some(tx),
                 tx_info.block_hash.unpack(),
                 cycles,
+                None,
             ));
         }
 
diff --git a/rpc/src/module/pool.rs b/rpc/src/module/pool.rs
index dfd4d9531d..1fe3e45de6 100644
--- a/rpc/src/module/pool.rs
+++ b/rpc/src/module/pool.rs
@@ -166,6 +166,7 @@ pub trait PoolRpc {
     ///   "result": {
     ///     "last_txs_updated_at": "0x0",
     ///     "min_fee_rate": "0x3e8",
+    ///     "min_rbf_rate": "0x5dc",
     ///     "max_tx_pool_size": "0xaba9500",
     ///     "orphan": "0x0",
     ///     "pending": "0x1",
diff --git a/sync/src/synchronizer/mod.rs b/sync/src/synchronizer/mod.rs
index b348226560..7f0a78c757 100644
--- a/sync/src/synchronizer/mod.rs
+++ b/sync/src/synchronizer/mod.rs
@@ -1,10 +1,10 @@
 //! CKB node has initial block download phase (IBD mode) like Bitcoin:
-//! https://btcinformation.org/en/glossary/initial-block-download
+//! <https://btcinformation.org/en/glossary/initial-block-download>
 //!
 //! When CKB node is in IBD mode, it will respond `packed::InIBD` to `GetHeaders` and `GetBlocks` requests
 //!
 //! And CKB has a headers-first synchronization style like Bitcoin:
-//! https://btcinformation.org/en/glossary/headers-first-sync
+//! <https://btcinformation.org/en/glossary/headers-first-sync>
 //!
 mod block_fetcher;
 mod block_process;
diff --git a/tx-pool/Cargo.toml b/tx-pool/Cargo.toml
index 04e465561a..c2c6c2ec67 100644
--- a/tx-pool/Cargo.toml
+++ b/tx-pool/Cargo.toml
@@ -36,7 +36,7 @@ sentry = { version = "0.26.0", optional = true }
 serde_json = "1.0"
 rand = "0.8.4"
 hyper = { version = "0.14", features = ["http1", "client", "tcp"] }
-ckb_multi_index_map = "0.0.2" # ckb team fork crate
+multi_index_map = "0.6.0"
 slab = "0.4"
 rustc-hash = "1.1"
 tokio-util = "0.7.8"
diff --git a/tx-pool/src/chunk_process.rs b/tx-pool/src/chunk_process.rs
index 73e4f246eb..51ebdec07d 100644
--- a/tx-pool/src/chunk_process.rs
+++ b/tx-pool/src/chunk_process.rs
@@ -226,7 +226,8 @@ impl ChunkProcess {
         let tx_hash = tx.hash();
 
         let (ret, snapshot) = self.service.pre_check(&tx).await;
-        let (tip_hash, rtx, status, fee, tx_size) = try_or_return_with_snapshot!(ret, snapshot);
+        let (tip_hash, rtx, status, fee, tx_size, conflicts) =
+            try_or_return_with_snapshot!(ret, snapshot);
 
         let cached = self.service.fetch_tx_verify_cache(&tx_hash).await;
 
@@ -251,8 +252,10 @@ impl ChunkProcess {
                     let completed = try_or_return_with_snapshot!(ret, snapshot);
 
                     let entry = TxEntry::new(rtx, completed.cycles, fee, tx_size);
-                    let (ret, submit_snapshot) =
-                        self.service.submit_entry(tip_hash, entry, status).await;
+                    let (ret, submit_snapshot) = self
+                        .service
+                        .submit_entry(tip_hash, entry, status, conflicts)
+                        .await;
                     try_or_return_with_snapshot!(ret, submit_snapshot);
                     self.service
                         .after_process(tx, remote, &submit_snapshot, &Ok(completed))
@@ -321,7 +324,10 @@ impl ChunkProcess {
         }
 
         let entry = TxEntry::new(rtx, completed.cycles, fee, tx_size);
-        let (ret, submit_snapshot) = self.service.submit_entry(tip_hash, entry, status).await;
+        let (ret, submit_snapshot) = self
+            .service
+            .submit_entry(tip_hash, entry, status, conflicts)
+            .await;
         try_or_return_with_snapshot!(ret, snapshot);
 
         self.service.notify_block_assembler(status).await;
diff --git a/tx-pool/src/component/commit_txs_scanner.rs b/tx-pool/src/component/commit_txs_scanner.rs
index c2058fdba6..7795a711c4 100644
--- a/tx-pool/src/component/commit_txs_scanner.rs
+++ b/tx-pool/src/component/commit_txs_scanner.rs
@@ -1,44 +1,45 @@
+extern crate slab;
 use crate::component::pool_map::PoolMap;
-use crate::component::{entry::TxEntry, score_key::AncestorsScoreSortKey};
+use crate::component::{entry::TxEntry, sort_key::AncestorsScoreSortKey};
 use ckb_types::{core::Cycle, packed::ProposalShortId};
 use ckb_util::LinkedHashMap;
-use std::collections::{BTreeSet, HashMap, HashSet};
+use multi_index_map::MultiIndexMap;
+use std::collections::HashSet;
 
 // A template data struct used to store modified entries when package txs
-#[derive(Default)]
-pub struct TxModifiedEntries {
-    entries: HashMap<ProposalShortId, TxEntry>,
-    sorted_index: BTreeSet<AncestorsScoreSortKey>,
+#[derive(MultiIndexMap, Clone)]
+pub struct ModifiedTx {
+    #[multi_index(hashed_unique)]
+    pub id: ProposalShortId,
+    #[multi_index(ordered_non_unique)]
+    pub score: AncestorsScoreSortKey,
+    pub inner: TxEntry,
 }
 
-impl TxModifiedEntries {
+impl MultiIndexModifiedTxMap {
     pub fn next_best_entry(&self) -> Option<&TxEntry> {
-        self.sorted_index
-            .iter()
-            .max()
-            .map(|key| self.entries.get(&key.id).expect("consistent"))
+        self.iter_by_score().last().map(|x| &x.inner)
     }
 
     pub fn get(&self, id: &ProposalShortId) -> Option<&TxEntry> {
-        self.entries.get(id)
+        self.get_by_id(id).map(|x| &x.inner)
     }
 
     pub fn contains_key(&self, id: &ProposalShortId) -> bool {
-        self.entries.contains_key(id)
+        self.get_by_id(id).is_some()
     }
 
-    pub fn insert(&mut self, entry: TxEntry) {
-        let key = AncestorsScoreSortKey::from(&entry);
-        let short_id = entry.proposal_short_id();
-        self.entries.insert(short_id, entry);
-        self.sorted_index.insert(key);
+    pub fn insert_entry(&mut self, entry: TxEntry) {
+        let score = AncestorsScoreSortKey::from(&entry);
+        self.insert(ModifiedTx {
+            id: entry.proposal_short_id(),
+            score,
+            inner: entry,
+        });
     }
 
     pub fn remove(&mut self, id: &ProposalShortId) -> Option<TxEntry> {
-        self.entries.remove(id).map(|entry| {
-            self.sorted_index.remove(&(&entry).into());
-            entry
-        })
+        self.remove_by_id(id).map(|x| x.inner)
     }
 }
 
@@ -53,7 +54,7 @@ pub struct CommitTxsScanner<'a> {
     entries: Vec<TxEntry>,
     // modified_entries will store sorted packages after they are modified
     // because some of their txs are already in the block
-    modified_entries: TxModifiedEntries,
+    modified_entries: MultiIndexModifiedTxMap,
     // txs that packaged in block
     fetched_txs: HashSet<ProposalShortId>,
     // Keep track of entries that failed inclusion, to avoid duplicate work
@@ -65,7 +66,7 @@ impl<'a> CommitTxsScanner<'a> {
         CommitTxsScanner {
             entries: Vec::new(),
             pool_map,
-            modified_entries: TxModifiedEntries::default(),
+            modified_entries: MultiIndexModifiedTxMap::default(),
             fetched_txs: HashSet::default(),
             failed_txs: HashSet::default(),
         }
@@ -210,7 +211,7 @@ impl<'a> CommitTxsScanner<'a> {
                     .or_else(|| self.pool_map.get(desc_id).cloned())
                 {
                     desc.sub_ancestor_weight(entry);
-                    self.modified_entries.insert(desc);
+                    self.modified_entries.insert_entry(desc);
                 }
             }
         }
diff --git a/tx-pool/src/component/entry.rs b/tx-pool/src/component/entry.rs
index 2f8fdf95ef..f45d4feace 100644
--- a/tx-pool/src/component/entry.rs
+++ b/tx-pool/src/component/entry.rs
@@ -1,4 +1,4 @@
-use crate::component::score_key::AncestorsScoreSortKey;
+use crate::component::sort_key::{AncestorsScoreSortKey, EvictKey};
 use ckb_systemtime::unix_time_as_millis;
 use ckb_types::{
     core::{
@@ -194,21 +194,6 @@ impl TxEntry {
     }
 }
 
-impl From<&TxEntry> for AncestorsScoreSortKey {
-    fn from(entry: &TxEntry) -> Self {
-        let weight = get_transaction_weight(entry.size, entry.cycles);
-        let ancestors_weight = get_transaction_weight(entry.ancestors_size, entry.ancestors_cycles);
-        AncestorsScoreSortKey {
-            fee: entry.fee,
-            weight,
-            id: entry.proposal_short_id(),
-            ancestors_fee: entry.ancestors_fee,
-            ancestors_weight,
-            //timestamp: entry.timestamp,
-        }
-    }
-}
-
 impl Hash for TxEntry {
     fn hash<H: Hasher>(&self, state: &mut H) {
         Hash::hash(self.transaction(), state);
@@ -233,14 +218,17 @@ impl Ord for TxEntry {
     }
 }
 
-/// First compare fee_rate, select the smallest fee_rate,
-/// and then select the latest timestamp, for eviction,
-/// the latest timestamp which also means that the fewer descendants may exist.
-#[derive(Eq, PartialEq, Clone, Debug)]
-pub struct EvictKey {
-    pub fee_rate: FeeRate,
-    pub timestamp: u64,
-    pub descendants_count: usize,
+impl From<&TxEntry> for AncestorsScoreSortKey {
+    fn from(entry: &TxEntry) -> Self {
+        let weight = get_transaction_weight(entry.size, entry.cycles);
+        let ancestors_weight = get_transaction_weight(entry.ancestors_size, entry.ancestors_cycles);
+        AncestorsScoreSortKey {
+            fee: entry.fee,
+            weight,
+            ancestors_fee: entry.ancestors_fee,
+            ancestors_weight,
+        }
+    }
 }
 
 impl From<&TxEntry> for EvictKey {
@@ -258,23 +246,3 @@ impl From<&TxEntry> for EvictKey {
         }
     }
 }
-
-impl PartialOrd for EvictKey {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
-impl Ord for EvictKey {
-    fn cmp(&self, other: &Self) -> Ordering {
-        if self.fee_rate == other.fee_rate {
-            if self.descendants_count == other.descendants_count {
-                self.timestamp.cmp(&other.timestamp)
-            } else {
-                self.descendants_count.cmp(&other.descendants_count)
-            }
-        } else {
-            self.fee_rate.cmp(&other.fee_rate)
-        }
-    }
-}
diff --git a/tx-pool/src/component/mod.rs b/tx-pool/src/component/mod.rs
index 7f325424ba..e5b8ab3cfc 100644
--- a/tx-pool/src/component/mod.rs
+++ b/tx-pool/src/component/mod.rs
@@ -7,7 +7,7 @@ pub(crate) mod links;
 pub(crate) mod orphan;
 pub(crate) mod pool_map;
 pub(crate) mod recent_reject;
-pub(crate) mod score_key;
+pub(crate) mod sort_key;
 
 #[cfg(test)]
 mod tests;
diff --git a/tx-pool/src/component/pool_map.rs b/tx-pool/src/component/pool_map.rs
index ce2c05bb0c..a0830a42d4 100644
--- a/tx-pool/src/component/pool_map.rs
+++ b/tx-pool/src/component/pool_map.rs
@@ -2,24 +2,21 @@
 extern crate rustc_hash;
 extern crate slab;
 use crate::component::edges::Edges;
-use crate::component::entry::EvictKey;
 use crate::component::links::{Relation, TxLinksMap};
-use crate::component::score_key::AncestorsScoreSortKey;
+use crate::component::sort_key::{AncestorsScoreSortKey, EvictKey};
 use crate::error::Reject;
 use crate::TxEntry;
-use ckb_logger::{debug, trace};
-use ckb_multi_index_map::MultiIndexMap;
+
+use ckb_logger::trace;
 use ckb_types::core::error::OutPointError;
 use ckb_types::packed::OutPoint;
+use ckb_types::prelude::*;
 use ckb_types::{
     bytes::Bytes,
-    core::{cell::CellChecker, TransactionView},
+    core::TransactionView,
     packed::{Byte32, CellOutput, ProposalShortId},
 };
-use ckb_types::{
-    core::cell::{CellMetaBuilder, CellProvider, CellStatus},
-    prelude::*,
-};
+use multi_index_map::MultiIndexMap;
 use std::collections::HashSet;
 
 use super::links::TxLinks;
@@ -45,7 +42,7 @@ pub struct PoolEntry {
     pub id: ProposalShortId,
     #[multi_index(ordered_non_unique)]
     pub score: AncestorsScoreSortKey,
-    #[multi_index(ordered_non_unique)]
+    #[multi_index(hashed_non_unique)]
     pub status: Status,
     #[multi_index(ordered_non_unique)]
     pub evict_key: EvictKey,
@@ -114,6 +111,10 @@ impl PoolMap {
         self.entries.get_by_id(id)
     }
 
+    fn get_by_id_checked(&self, id: &ProposalShortId) -> &PoolEntry {
+        self.get_by_id(id).expect("unconsistent pool")
+    }
+
     pub(crate) fn get_by_status(&self, status: Status) -> Vec<&PoolEntry> {
         self.entries.get_by_status(&status)
     }
@@ -171,9 +172,9 @@ impl PoolMap {
             return Ok(false);
         }
         trace!("pool_map.add_{:?} {}", status, entry.transaction().hash());
-        self.check_record_ancestors(&mut entry)?;
+        self.check_and_record_ancestors(&mut entry)?;
         self.insert_entry(&entry, status);
-        self.record_entry_deps(&entry);
+        self.record_entry_edges(&entry);
         self.record_entry_descendants(&entry);
         Ok(true)
     }
@@ -191,7 +192,6 @@ impl PoolMap {
         self.entries.remove_by_id(id).map(|entry| {
             self.update_ancestors_index_key(&entry.inner, EntryOp::Remove);
             self.update_descendants_index_key(&entry.inner, EntryOp::Remove);
-            self.remove_entry_deps(&entry.inner);
             self.remove_entry_edges(&entry.inner);
             self.remove_entry_links(id);
             entry.inner
@@ -240,11 +240,16 @@ impl PoolMap {
         conflicts
     }
 
+    pub(crate) fn find_conflict_tx(&self, tx: &TransactionView) -> HashSet<ProposalShortId> {
+        tx.input_pts_iter()
+            .filter_map(|out_point| self.edges.get_input_ref(&out_point).cloned())
+            .collect()
+    }
+
     pub(crate) fn resolve_conflict(&mut self, tx: &TransactionView) -> Vec<ConflictEntry> {
-        let inputs = tx.input_pts_iter();
         let mut conflicts = Vec::new();
 
-        for i in inputs {
+        for i in tx.input_pts_iter() {
             if let Some(id) = self.edges.remove_input(&i) {
                 let entries = self.remove_entry_and_descendants(&id);
                 if !entries.is_empty() {
@@ -361,7 +366,7 @@ impl PoolMap {
         }
     }
 
-    fn record_entry_deps(&mut self, entry: &TxEntry) {
+    fn record_entry_edges(&mut self, entry: &TxEntry) {
         let tx_short_id: ProposalShortId = entry.proposal_short_id();
         let header_deps = entry.transaction().header_deps();
         let related_dep_out_points: Vec<_> = entry.related_dep_out_points().cloned().collect();
@@ -414,7 +419,7 @@ impl PoolMap {
     }
 
     /// Check ancestors and record for entry
-    fn check_record_ancestors(&mut self, entry: &mut TxEntry) -> Result<bool, Reject> {
+    fn check_and_record_ancestors(&mut self, entry: &mut TxEntry) -> Result<bool, Reject> {
         let mut parents: HashSet<ProposalShortId> = HashSet::with_capacity(
             entry.transaction().inputs().len() + entry.transaction().cell_deps().len(),
         );
@@ -446,14 +451,10 @@ impl PoolMap {
 
         // update parents references
         for ancestor_id in &ancestors {
-            let ancestor = self
-                .entries
-                .get_by_id(ancestor_id)
-                .expect("pool consistent");
+            let ancestor = self.get_by_id_checked(ancestor_id);
             entry.add_ancestor_weight(&ancestor.inner);
         }
         if entry.ancestors_count > self.max_ancestors_count {
-            debug!("debug: exceeded maximum ancestors count");
             return Err(Reject::ExceededMaximumAncestorsCount);
         }
 
@@ -476,9 +477,6 @@ impl PoolMap {
             // release input record
             self.edges.remove_input(&i);
         }
-    }
-
-    fn remove_entry_deps(&mut self, entry: &TxEntry) {
         let id = entry.proposal_short_id();
         for d in entry.related_dep_out_points().cloned() {
             self.edges.delete_txid_by_dep(d, &id);
@@ -500,31 +498,3 @@ impl PoolMap {
         });
     }
 }
-
-impl CellProvider for PoolMap {
-    fn cell(&self, out_point: &OutPoint, _eager_load: bool) -> CellStatus {
-        if self.edges.get_input_ref(out_point).is_some() {
-            return CellStatus::Dead;
-        }
-        if let Some((output, data)) = self.get_output_with_data(out_point) {
-            let cell_meta = CellMetaBuilder::from_cell_output(output, data)
-                .out_point(out_point.to_owned())
-                .build();
-            CellStatus::live_cell(cell_meta)
-        } else {
-            CellStatus::Unknown
-        }
-    }
-}
-
-impl CellChecker for PoolMap {
-    fn is_live(&self, out_point: &OutPoint) -> Option<bool> {
-        if self.edges.get_input_ref(out_point).is_some() {
-            return Some(false);
-        }
-        if self.get_output_with_data(out_point).is_some() {
-            return Some(true);
-        }
-        None
-    }
-}
diff --git a/tx-pool/src/component/sort_key.rs b/tx-pool/src/component/sort_key.rs
new file mode 100644
index 0000000000..ceeab649bc
--- /dev/null
+++ b/tx-pool/src/component/sort_key.rs
@@ -0,0 +1,78 @@
+use ckb_types::core::{Capacity, FeeRate};
+use std::cmp::Ordering;
+
+/// A struct to use as a sorted key
+#[derive(Eq, PartialEq, Clone, Debug)]
+pub struct AncestorsScoreSortKey {
+    pub fee: Capacity,
+    pub weight: u64,
+    pub ancestors_fee: Capacity,
+    pub ancestors_weight: u64,
+}
+
+impl AncestorsScoreSortKey {
+    /// compare tx fee rate with ancestors fee rate and return the min one
+    pub(crate) fn min_fee_and_weight(&self) -> (Capacity, u64) {
+        // avoid division a_fee/a_weight > b_fee/b_weight
+        let tx_weight = u128::from(self.fee.as_u64()) * u128::from(self.ancestors_weight);
+        let ancestors_weight = u128::from(self.ancestors_fee.as_u64()) * u128::from(self.weight);
+
+        if tx_weight < ancestors_weight {
+            (self.fee, self.weight)
+        } else {
+            (self.ancestors_fee, self.ancestors_weight)
+        }
+    }
+}
+
+impl PartialOrd for AncestorsScoreSortKey {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for AncestorsScoreSortKey {
+    fn cmp(&self, other: &Self) -> Ordering {
+        // avoid division a_fee/a_weight > b_fee/b_weight
+        let (fee, weight) = self.min_fee_and_weight();
+        let (other_fee, other_weight) = other.min_fee_and_weight();
+        let self_weight = u128::from(fee.as_u64()) * u128::from(other_weight);
+        let other_weight = u128::from(other_fee.as_u64()) * u128::from(weight);
+        if self_weight == other_weight {
+            // if fee rate weight is same, then compare with ancestor weight
+            self.ancestors_weight.cmp(&other.ancestors_weight)
+        } else {
+            self_weight.cmp(&other_weight)
+        }
+    }
+}
+
+/// First compare fee_rate, select the smallest fee_rate,
+/// and then select the latest timestamp, for eviction,
+/// the latest timestamp which also means that the fewer descendants may exist.
+#[derive(Eq, PartialEq, Clone, Debug)]
+pub struct EvictKey {
+    pub fee_rate: FeeRate,
+    pub timestamp: u64,
+    pub descendants_count: usize,
+}
+
+impl PartialOrd for EvictKey {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for EvictKey {
+    fn cmp(&self, other: &Self) -> Ordering {
+        if self.fee_rate == other.fee_rate {
+            if self.descendants_count == other.descendants_count {
+                self.timestamp.cmp(&other.timestamp)
+            } else {
+                self.descendants_count.cmp(&other.descendants_count)
+            }
+        } else {
+            self.fee_rate.cmp(&other.fee_rate)
+        }
+    }
+}
diff --git a/tx-pool/src/lib.rs b/tx-pool/src/lib.rs
index 48a2157679..d122177c01 100644
--- a/tx-pool/src/lib.rs
+++ b/tx-pool/src/lib.rs
@@ -8,6 +8,7 @@ mod component;
 pub mod error;
 mod persisted;
 pub mod pool;
+mod pool_cell;
 mod process;
 pub mod service;
 mod util;
diff --git a/tx-pool/src/pool.rs b/tx-pool/src/pool.rs
index ae101e68a5..b7952f4838 100644
--- a/tx-pool/src/pool.rs
+++ b/tx-pool/src/pool.rs
@@ -6,15 +6,17 @@ use crate::callback::Callbacks;
 use crate::component::pool_map::{PoolEntry, PoolMap, Status};
 use crate::component::recent_reject::RecentReject;
 use crate::error::Reject;
+use crate::pool_cell::PoolCell;
 use ckb_app_config::TxPoolConfig;
 use ckb_logger::{debug, error, warn};
 use ckb_snapshot::Snapshot;
 use ckb_store::ChainStore;
+use ckb_types::core::CapacityError;
 use ckb_types::{
     core::{
         cell::{resolve_transaction, OverlayCellChecker, OverlayCellProvider, ResolvedTransaction},
         tx_pool::{TxPoolEntryInfo, TxPoolIds},
-        Cycle, TransactionView, UncleBlockView,
+        Capacity, Cycle, TransactionView, UncleBlockView,
     },
     packed::{Byte32, ProposalShortId},
 };
@@ -23,6 +25,7 @@ use std::collections::HashSet;
 use std::sync::Arc;
 
 const COMMITTED_HASH_CACHE_SIZE: usize = 100_000;
+const MAX_REPLACEMENT_CANDIDATES: usize = 100;
 
 /// Tx-pool implementation
 pub struct TxPool {
@@ -84,6 +87,44 @@ impl TxPool {
         self.total_tx_cycles += cycles;
     }
 
+    /// Check whether tx-pool enable RBF
+    pub fn enable_rbf(&self) -> bool {
+        self.config.min_rbf_rate > self.config.min_fee_rate
+    }
+
+    /// The least required fee rate to allow tx to be replaced
+    pub fn min_replace_fee(&self, tx: &TxEntry) -> Option<Capacity> {
+        if !self.enable_rbf() {
+            return None;
+        }
+        let entry = vec![self.get_pool_entry(&tx.proposal_short_id()).unwrap()];
+        self.calculate_min_replace_fee(&entry, tx.size)
+    }
+
+    /// min_replace_fee = sum(replaced_txs.fee) + extra_rbf_fee
+    fn calculate_min_replace_fee(&self, conflicts: &[&PoolEntry], size: usize) -> Option<Capacity> {
+        let extra_rbf_fee = self.config.min_rbf_rate.fee(size as u64);
+        let replaced_sum_fee = conflicts
+            .iter()
+            .map(|c| c.inner.fee)
+            .try_fold(Capacity::zero(), |acc, x| acc.safe_add(x));
+        let res = replaced_sum_fee.map_or(Err(CapacityError::Overflow), |sum| {
+            sum.safe_add(extra_rbf_fee)
+        });
+        if let Ok(res) = res {
+            Some(res)
+        } else {
+            let fees = conflicts.iter().map(|c| c.inner.fee).collect::<Vec<_>>();
+            error!(
+                "conflicts: {:?} replaced_sum_fee {:?} overflow by add {}",
+                conflicts.iter().map(|e| e.id.clone()).collect::<Vec<_>>(),
+                fees,
+                extra_rbf_fee
+            );
+            None
+        }
+    }
+
     /// Update size and cycles statics for remove tx
     /// cycles overflow is possible, currently obtaining cycles is not accurate
     pub fn update_statics_for_remove_tx(&mut self, tx_size: usize, cycles: Cycle) {
@@ -287,7 +328,8 @@ impl TxPool {
 
     pub(crate) fn check_rtx_from_pool(&self, rtx: &ResolvedTransaction) -> Result<(), Reject> {
         let snapshot = self.snapshot();
-        let checker = OverlayCellChecker::new(&self.pool_map, snapshot);
+        let pool_cell = PoolCell::new(&self.pool_map, false);
+        let checker = OverlayCellChecker::new(&pool_cell, snapshot);
         let mut seen_inputs = HashSet::new();
         rtx.check(&mut seen_inputs, &checker, snapshot)
             .map_err(Reject::Resolve)
@@ -296,9 +338,11 @@ impl TxPool {
     pub(crate) fn resolve_tx_from_pool(
         &self,
         tx: TransactionView,
+        rbf: bool,
     ) -> Result<Arc<ResolvedTransaction>, Reject> {
         let snapshot = self.snapshot();
-        let provider = OverlayCellProvider::new(&self.pool_map, snapshot);
+        let pool_cell = PoolCell::new(&self.pool_map, rbf);
+        let provider = OverlayCellProvider::new(&pool_cell, snapshot);
         let mut seen_inputs = HashSet::new();
         resolve_transaction(tx, &mut seen_inputs, &provider, snapshot)
             .map(Arc::new)
@@ -346,8 +390,6 @@ impl TxPool {
         let mut proposals = HashSet::with_capacity(limit);
         self.pool_map
             .fill_proposals(limit, exclusion, &mut proposals, Status::Pending);
-        self.pool_map
-            .fill_proposals(limit, exclusion, &mut proposals, Status::Gap);
         proposals
     }
 
@@ -465,6 +507,110 @@ impl TxPool {
         (entries, size, cycles)
     }
 
+    pub(crate) fn check_rbf(
+        &self,
+        snapshot: &Snapshot,
+        rtx: &ResolvedTransaction,
+        conflict_ids: &HashSet<ProposalShortId>,
+        fee: Capacity,
+        tx_size: usize,
+    ) -> Result<(), Reject> {
+        assert!(self.enable_rbf());
+        assert!(!conflict_ids.is_empty());
+
+        let conflicts = conflict_ids
+            .iter()
+            .filter_map(|id| self.get_pool_entry(id))
+            .collect::<Vec<_>>();
+        assert!(conflicts.len() == conflict_ids.len());
+
+        let short_id = rtx.transaction.proposal_short_id();
+        // Rule #4, new tx's fee need to higher than min_rbf_fee computed from the tx_pool configuration
+        // Rule #3, new tx's fee need to higher than conflicts, here we only check the root tx
+        if let Some(min_replace_fee) = self.calculate_min_replace_fee(&conflicts, tx_size) {
+            if fee < min_replace_fee {
+                return Err(Reject::RBFRejected(format!(
+                    "Tx's current fee is {}, expect it to >= {} to replace old txs",
+                    fee, min_replace_fee,
+                )));
+            }
+        } else {
+            return Err(Reject::RBFRejected(
+                "calculate_min_replace_fee failed".to_string(),
+            ));
+        }
+
+        // Rule #2, new tx don't contain any new unconfirmed inputs
+        let mut inputs = HashSet::new();
+        for c in conflicts.iter() {
+            inputs.extend(c.inner.transaction().input_pts_iter());
+        }
+
+        if rtx
+            .transaction
+            .input_pts_iter()
+            .any(|pt| !inputs.contains(&pt) && !snapshot.transaction_exists(&pt.tx_hash()))
+        {
+            return Err(Reject::RBFRejected(
+                "new Tx contains unconfirmed inputs".to_string(),
+            ));
+        }
+
+        // Rule #5, the replaced tx's descendants can not more than 100
+        // and the ancestor of the new tx don't have common set with the replaced tx's descendants
+        let mut replace_count: usize = 0;
+        let ancestors = self.pool_map.calc_ancestors(&short_id);
+        for conflict in conflicts.iter() {
+            let descendants = self.pool_map.calc_descendants(&conflict.id);
+            replace_count += descendants.len() + 1;
+            if replace_count > MAX_REPLACEMENT_CANDIDATES {
+                return Err(Reject::RBFRejected(format!(
+                    "Tx conflict too many txs, conflict txs count: {}",
+                    replace_count,
+                )));
+            }
+
+            if !descendants.is_disjoint(&ancestors) {
+                return Err(Reject::RBFRejected(
+                    "Tx ancestors have common with conflict Tx descendants".to_string(),
+                ));
+            }
+
+            let entries = descendants
+                .iter()
+                .filter_map(|id| self.get_pool_entry(id))
+                .collect::<Vec<_>>();
+
+            for entry in entries.iter() {
+                let hash = entry.inner.transaction().hash();
+                if rtx
+                    .transaction
+                    .input_pts_iter()
+                    .any(|pt| pt.tx_hash() == hash)
+                {
+                    return Err(Reject::RBFRejected(
+                        "new Tx contains inputs in descendants of to be replaced Tx".to_string(),
+                    ));
+                }
+            }
+
+            let mut entries_status = entries.iter().map(|e| e.status).collect::<Vec<_>>();
+            entries_status.push(conflict.status);
+            // Rule #6, all conflict Txs should be in `Pending` or `Gap` status
+            if entries_status
+                .iter()
+                .any(|s| ![Status::Pending, Status::Gap].contains(s))
+            {
+                // Here we only refer to `Pending` status, since `Gap` is an internal status
+                return Err(Reject::RBFRejected(
+                    "all conflict Txs should be in Pending status".to_string(),
+                ));
+            }
+        }
+
+        Ok(())
+    }
+
     fn build_recent_reject(config: &TxPoolConfig) -> Option<RecentReject> {
         if !config.recent_reject.as_os_str().is_empty() {
             let recent_reject_ttl =
diff --git a/tx-pool/src/pool_cell.rs b/tx-pool/src/pool_cell.rs
new file mode 100644
index 0000000000..4e70d44c82
--- /dev/null
+++ b/tx-pool/src/pool_cell.rs
@@ -0,0 +1,44 @@
+extern crate rustc_hash;
+extern crate slab;
+use crate::component::pool_map::PoolMap;
+use ckb_types::core::cell::{CellChecker, CellMetaBuilder, CellProvider, CellStatus};
+use ckb_types::packed::OutPoint;
+
+pub(crate) struct PoolCell<'a> {
+    pub pool_map: &'a PoolMap,
+    pub rbf: bool,
+}
+
+impl<'a> PoolCell<'a> {
+    pub fn new(pool_map: &'a PoolMap, rbf: bool) -> Self {
+        PoolCell { pool_map, rbf }
+    }
+}
+
+impl<'a> CellProvider for PoolCell<'a> {
+    fn cell(&self, out_point: &OutPoint, _eager_load: bool) -> CellStatus {
+        if !self.rbf && self.pool_map.edges.get_input_ref(out_point).is_some() {
+            return CellStatus::Dead;
+        }
+        if let Some((output, data)) = self.pool_map.get_output_with_data(out_point) {
+            let cell_meta = CellMetaBuilder::from_cell_output(output, data)
+                .out_point(out_point.to_owned())
+                .build();
+            CellStatus::live_cell(cell_meta)
+        } else {
+            CellStatus::Unknown
+        }
+    }
+}
+
+impl<'a> CellChecker for PoolCell<'a> {
+    fn is_live(&self, out_point: &OutPoint) -> Option<bool> {
+        if !self.rbf && self.pool_map.edges.get_input_ref(out_point).is_some() {
+            return Some(false);
+        }
+        if self.pool_map.get_output_with_data(out_point).is_some() {
+            return Some(true);
+        }
+        None
+    }
+}
diff --git a/tx-pool/src/process.rs b/tx-pool/src/process.rs
index e921203aff..c386bd0524 100644
--- a/tx-pool/src/process.rs
+++ b/tx-pool/src/process.rs
@@ -19,6 +19,7 @@ use ckb_network::PeerIndex;
 use ckb_snapshot::Snapshot;
 use ckb_store::data_loader_wrapper::AsDataLoader;
 use ckb_store::ChainStore;
+use ckb_types::core::error::OutPointError;
 use ckb_types::{
     core::{cell::ResolvedTransaction, BlockView, Capacity, Cycle, HeaderView, TransactionView},
     packed::{Byte32, ProposalShortId},
@@ -101,6 +102,7 @@ impl TxPoolService {
         pre_resolve_tip: Byte32,
         entry: TxEntry,
         mut status: TxStatus,
+        conflicts: HashSet<ProposalShortId>,
     ) -> (Result<(), Reject>, Arc<Snapshot>) {
         let (ret, snapshot) = self
             .with_tx_pool_write_lock(move |tx_pool, snapshot| {
@@ -123,6 +125,19 @@ impl TxPoolService {
                     time_relative_verify(snapshot, Arc::clone(&entry.rtx), tx_env)?;
                 }
 
+                // try to remove conflicted tx here
+                for id in conflicts.iter() {
+                    let removed = tx_pool.pool_map.remove_entry_and_descendants(id);
+                    for old in removed {
+                        let reject = Reject::RBFRejected(format!(
+                            "replaced by {}",
+                            entry.proposal_short_id()
+                        ));
+                        // remove old tx from tx_pool, not happened in service so we didn't call reject callbacks
+                        // here we call them manually
+                        self.callbacks.call_reject(tx_pool, &old, reject)
+                    }
+                }
                 _submit_entry(tx_pool, status, entry.clone(), &self.callbacks)?;
                 Ok(())
             })
@@ -202,13 +217,36 @@ impl TxPoolService {
             .with_tx_pool_read_lock(|tx_pool, snapshot| {
                 let tip_hash = snapshot.tip_hash();
 
+                // Same txid means exactly the same transaction, including inputs, outputs, witnesses, etc.
+                // It's also not possible for RBF, reject it directly
                 check_txid_collision(tx_pool, tx)?;
 
-                let (rtx, status) = resolve_tx(tx_pool, &snapshot, tx.clone())?;
-
-                let fee = check_tx_fee(tx_pool, &snapshot, &rtx, tx_size)?;
-
-                Ok((tip_hash, rtx, status, fee, tx_size))
+                // Try normal path first, if double-spending check success we don't need RBF check
+                // this make sure RBF won't introduce extra performance cost for hot path
+                let res = resolve_tx(tx_pool, &snapshot, tx.clone(), false);
+                match res {
+                    Ok((rtx, status)) => {
+                        let fee = check_tx_fee(tx_pool, &snapshot, &rtx, tx_size)?;
+                        Ok((tip_hash, rtx, status, fee, tx_size, HashSet::new()))
+                    }
+                    Err(err) => {
+                        if tx_pool.enable_rbf()
+                            && matches!(err, Reject::Resolve(OutPointError::Dead(_)))
+                        {
+                            // Try RBF check
+                            let conflicts = tx_pool.pool_map.find_conflict_tx(tx);
+                            if conflicts.is_empty() {
+                                return Err(err);
+                            }
+                            let (rtx, status) = resolve_tx(tx_pool, &snapshot, tx.clone(), true)?;
+                            let fee = check_tx_fee(tx_pool, &snapshot, &rtx, tx_size)?;
+                            tx_pool.check_rbf(&snapshot, &rtx, &conflicts, fee, tx_size)?;
+                            Ok((tip_hash, rtx, status, fee, tx_size, conflicts))
+                        } else {
+                            Err(err)
+                        }
+                    }
+                }
             })
             .await;
 
@@ -372,7 +410,12 @@ impl TxPoolService {
                             });
                         }
 
-                        if matches!(reject, Reject::Resolve(..) | Reject::Verification(..)) {
+                        if matches!(
+                            reject,
+                            Reject::Resolve(..)
+                                | Reject::Verification(..)
+                                | Reject::RBFRejected(..)
+                        ) {
                             self.put_recent_reject(&tx_hash, reject).await;
                         }
                     }
@@ -397,7 +440,12 @@ impl TxPoolService {
                         });
                     }
                     Err(reject) => {
-                        if matches!(reject, Reject::Resolve(..) | Reject::Verification(..)) {
+                        if matches!(
+                            reject,
+                            Reject::Resolve(..)
+                                | Reject::Verification(..)
+                                | Reject::RBFRejected(..)
+                        ) {
                             self.put_recent_reject(&tx_hash, reject).await;
                         }
                     }
@@ -497,8 +545,12 @@ impl TxPoolService {
                                         tx_hash: orphan.tx.hash(),
                                     });
                                 }
-                                if matches!(reject, Reject::Resolve(..) | Reject::Verification(..))
-                                {
+                                if matches!(
+                                    reject,
+                                    Reject::Resolve(..)
+                                        | Reject::Verification(..)
+                                        | Reject::RBFRejected(..)
+                                ) {
                                     self.put_recent_reject(&orphan.tx.hash(), &reject).await;
                                 }
                             }
@@ -550,7 +602,8 @@ impl TxPoolService {
         let tx_hash = tx.hash();
 
         let (ret, snapshot) = self.pre_check(&tx).await;
-        let (tip_hash, rtx, status, fee, tx_size) = try_or_return_with_snapshot!(ret, snapshot);
+        let (tip_hash, rtx, status, fee, tx_size, conflicts) =
+            try_or_return_with_snapshot!(ret, snapshot);
 
         if self.is_in_delay_window(&snapshot) {
             let mut delay = self.delay.write().await;
@@ -634,7 +687,7 @@ impl TxPoolService {
 
         let entry = TxEntry::new(rtx, completed.cycles, fee, tx_size);
 
-        let (ret, submit_snapshot) = self.submit_entry(tip_hash, entry, status).await;
+        let (ret, submit_snapshot) = self.submit_entry(tip_hash, entry, status, conflicts).await;
         try_or_return_with_snapshot!(ret, submit_snapshot);
 
         self.notify_block_assembler(status).await;
@@ -679,7 +732,8 @@ impl TxPoolService {
 
         let (ret, snapshot) = self.pre_check(&tx).await;
 
-        let (tip_hash, rtx, status, fee, tx_size) = try_or_return_with_snapshot!(ret, snapshot);
+        let (tip_hash, rtx, status, fee, tx_size, conflicts) =
+            try_or_return_with_snapshot!(ret, snapshot);
 
         if self.is_in_delay_window(&snapshot) {
             let mut delay = self.delay.write().await;
@@ -715,7 +769,7 @@ impl TxPoolService {
 
         let entry = TxEntry::new(rtx, verified.cycles, fee, tx_size);
 
-        let (ret, submit_snapshot) = self.submit_entry(tip_hash, entry, status).await;
+        let (ret, submit_snapshot) = self.submit_entry(tip_hash, entry, status, conflicts).await;
         try_or_return_with_snapshot!(ret, submit_snapshot);
 
         self.notify_block_assembler(status).await;
@@ -872,7 +926,7 @@ impl TxPoolService {
         for tx in txs {
             let tx_size = tx.data().serialized_size_in_block();
             let tx_hash = tx.hash();
-            if let Ok((rtx, status)) = resolve_tx(tx_pool, tx_pool.snapshot(), tx) {
+            if let Ok((rtx, status)) = resolve_tx(tx_pool, tx_pool.snapshot(), tx, false) {
                 if let Ok(fee) = check_tx_fee(tx_pool, tx_pool.snapshot(), &rtx, tx_size) {
                     let verify_cache = fetched_cache.get(&tx_hash).cloned();
                     let snapshot = tx_pool.cloned_snapshot();
@@ -949,36 +1003,50 @@ impl TxPoolService {
     }
 }
 
-type PreCheckedTx = (Byte32, Arc<ResolvedTransaction>, TxStatus, Capacity, usize);
+type PreCheckedTx = (
+    Byte32,                   // tip_hash
+    Arc<ResolvedTransaction>, // rtx
+    TxStatus,                 // status
+    Capacity,                 // tx fee
+    usize,                    // tx size
+    // the conflicted txs, used for latter `check_rbf`
+    // the root txs for removing from `tx-pool` when RBF is checked
+    HashSet<ProposalShortId>,
+);
 
 type ResolveResult = Result<(Arc<ResolvedTransaction>, TxStatus), Reject>;
 
+fn get_tx_status(snapshot: &Snapshot, short_id: &ProposalShortId) -> TxStatus {
+    if snapshot.proposals().contains_proposed(short_id) {
+        TxStatus::Proposed
+    } else if snapshot.proposals().contains_gap(short_id) {
+        TxStatus::Gap
+    } else {
+        TxStatus::Fresh
+    }
+}
+
 fn check_rtx(
     tx_pool: &TxPool,
     snapshot: &Snapshot,
     rtx: &ResolvedTransaction,
 ) -> Result<TxStatus, Reject> {
     let short_id = rtx.transaction.proposal_short_id();
-    let tx_status = if snapshot.proposals().contains_proposed(&short_id) {
-        TxStatus::Proposed
-    } else if snapshot.proposals().contains_gap(&short_id) {
-        TxStatus::Gap
-    } else {
-        TxStatus::Fresh
-    };
+    let tx_status = get_tx_status(snapshot, &short_id);
     tx_pool.check_rtx_from_pool(rtx).map(|_| tx_status)
 }
 
-fn resolve_tx(tx_pool: &TxPool, snapshot: &Snapshot, tx: TransactionView) -> ResolveResult {
+fn resolve_tx(
+    tx_pool: &TxPool,
+    snapshot: &Snapshot,
+    tx: TransactionView,
+    rbf: bool,
+) -> ResolveResult {
     let short_id = tx.proposal_short_id();
-    let tx_status = if snapshot.proposals().contains_proposed(&short_id) {
-        TxStatus::Proposed
-    } else if snapshot.proposals().contains_gap(&short_id) {
-        TxStatus::Gap
-    } else {
-        TxStatus::Fresh
-    };
-    tx_pool.resolve_tx_from_pool(tx).map(|rtx| (rtx, tx_status))
+    let tx_status = get_tx_status(snapshot, &short_id);
+    tx_pool
+        .resolve_tx_from_pool(tx, rbf)
+        .map(|rtx| (rtx, tx_status))
 }
 
 fn _submit_entry(
diff --git a/tx-pool/src/service.rs b/tx-pool/src/service.rs
index 1a187615c8..9df681f071 100644
--- a/tx-pool/src/service.rs
+++ b/tx-pool/src/service.rs
@@ -779,26 +779,24 @@ async fn process(mut service: TxPoolService, message: Message) {
                 ..
             }) = tx_pool.pool_map.get_by_id(&id)
             {
-                let trans_status = if status == &Status::Proposed {
-                    TransactionWithStatus::with_proposed
+                let (tx_status, min_replace_fee) = if status == &Status::Proposed {
+                    (TxStatus::Proposed, None)
                 } else {
-                    TransactionWithStatus::with_pending
+                    (TxStatus::Pending, tx_pool.min_replace_fee(entry))
                 };
-                Ok(trans_status(
+                Ok(TransactionWithStatus::with_status(
                     Some(entry.transaction().clone()),
                     entry.cycles,
                     entry.timestamp,
+                    tx_status,
+                    Some(entry.fee),
+                    min_replace_fee,
                 ))
             } else if let Some(ref recent_reject_db) = tx_pool.recent_reject {
-                let recent_reject_result = recent_reject_db.get(&hash);
-                if let Ok(recent_reject) = recent_reject_result {
-                    if let Some(record) = recent_reject {
-                        Ok(TransactionWithStatus::with_rejected(record))
-                    } else {
-                        Ok(TransactionWithStatus::with_unknown())
-                    }
-                } else {
-                    Err(recent_reject_result.unwrap_err())
+                match recent_reject_db.get(&hash) {
+                    Ok(Some(record)) => Ok(TransactionWithStatus::with_rejected(record)),
+                    Ok(_) => Ok(TransactionWithStatus::with_unknown()),
+                    Err(err) => Err(err),
                 }
             } else {
                 Ok(TransactionWithStatus::with_unknown())
@@ -919,6 +917,7 @@ impl TxPoolService {
             total_tx_size: tx_pool.total_tx_size,
             total_tx_cycles: tx_pool.total_tx_cycles,
             min_fee_rate: self.tx_pool_config.min_fee_rate,
+            min_rbf_rate: self.tx_pool_config.min_rbf_rate,
             last_txs_updated_at: 0,
             tx_size_limit: TRANSACTION_SIZE_LIMIT,
             max_tx_pool_size: self.tx_pool_config.max_tx_pool_size as u64,
diff --git a/util/app-config/src/configs/tx_pool.rs b/util/app-config/src/configs/tx_pool.rs
index b71223ef7e..a24c7938de 100644
--- a/util/app-config/src/configs/tx_pool.rs
+++ b/util/app-config/src/configs/tx_pool.rs
@@ -14,6 +14,9 @@ pub struct TxPoolConfig {
     /// txs with lower fee rate than this will not be relayed or be mined
     #[serde(with = "FeeRateDef")]
     pub min_fee_rate: FeeRate,
+    /// txs need to pay larger fee rate than this for RBF
+    #[serde(with = "FeeRateDef")]
+    pub min_rbf_rate: FeeRate,
     /// tx pool rejects txs that cycles greater than max_tx_verify_cycles
     pub max_tx_verify_cycles: Cycle,
     /// max ancestors size limit for a single tx
diff --git a/util/app-config/src/legacy/tx_pool.rs b/util/app-config/src/legacy/tx_pool.rs
index bf82ecc1af..562f3ac6a6 100644
--- a/util/app-config/src/legacy/tx_pool.rs
+++ b/util/app-config/src/legacy/tx_pool.rs
@@ -7,6 +7,8 @@ use std::path::PathBuf;
 
 // default min fee rate, 1000 shannons per kilobyte
 const DEFAULT_MIN_FEE_RATE: FeeRate = FeeRate::from_u64(1000);
+// default min rbf rate, 1500 shannons per kilobyte
+const DEFAULT_MIN_RBF_RATE: FeeRate = FeeRate::from_u64(1500);
 // default max tx verify cycles
 const DEFAULT_MAX_TX_VERIFY_CYCLES: Cycle = TWO_IN_TWO_OUT_CYCLES * 20;
 // default max ancestors count
@@ -33,6 +35,8 @@ pub(crate) struct TxPoolConfig {
     keep_rejected_tx_hashes_count: u64,
     #[serde(with = "FeeRateDef")]
     min_fee_rate: FeeRate,
+    #[serde(with = "FeeRateDef", default = "default_min_rbf_rate")]
+    min_rbf_rate: FeeRate,
     max_tx_verify_cycles: Cycle,
     max_ancestors_count: usize,
     #[serde(default)]
@@ -59,6 +63,10 @@ fn default_max_tx_pool_size() -> usize {
     DEFAULT_MAX_TX_POOL_SIZE
 }
 
+fn default_min_rbf_rate() -> FeeRate {
+    DEFAULT_MIN_RBF_RATE
+}
+
 impl Default for crate::TxPoolConfig {
     fn default() -> Self {
         TxPoolConfig::default().into()
@@ -77,6 +85,7 @@ impl Default for TxPoolConfig {
             keep_rejected_tx_hashes_days: default_keep_rejected_tx_hashes_days(),
             keep_rejected_tx_hashes_count: default_keep_rejected_tx_hashes_count(),
             min_fee_rate: DEFAULT_MIN_FEE_RATE,
+            min_rbf_rate: DEFAULT_MIN_RBF_RATE,
             max_tx_verify_cycles: DEFAULT_MAX_TX_VERIFY_CYCLES,
             max_ancestors_count: DEFAULT_MAX_ANCESTORS_COUNT,
             persisted_data: Default::default(),
@@ -98,6 +107,7 @@ impl From<TxPoolConfig> for crate::TxPoolConfig {
             keep_rejected_tx_hashes_days,
             keep_rejected_tx_hashes_count,
             min_fee_rate,
+            min_rbf_rate,
             max_tx_verify_cycles,
             max_ancestors_count,
             persisted_data,
@@ -108,6 +118,7 @@ impl From<TxPoolConfig> for crate::TxPoolConfig {
         Self {
             max_tx_pool_size,
             min_fee_rate,
+            min_rbf_rate,
             max_tx_verify_cycles,
             max_ancestors_count: cmp::max(DEFAULT_MAX_ANCESTORS_COUNT, max_ancestors_count),
             keep_rejected_tx_hashes_days,
diff --git a/util/jsonrpc-types/src/blockchain.rs b/util/jsonrpc-types/src/blockchain.rs
index 8acaf95ce7..8d2824b445 100644
--- a/util/jsonrpc-types/src/blockchain.rs
+++ b/util/jsonrpc-types/src/blockchain.rs
@@ -534,6 +534,10 @@ pub struct TransactionWithStatusResponse {
     pub time_added_to_pool: Option<Uint64>,
     /// The Transaction status.
     pub tx_status: TxStatus,
+    /// The transaction fee of the transaction
+    pub fee: Option<Capacity>,
+    /// The minimal fee required to replace this transaction
+    pub min_replace_fee: Option<Capacity>,
 }
 
 impl TransactionWithStatusResponse {
@@ -548,6 +552,8 @@ impl TransactionWithStatusResponse {
                 tx_status: t.tx_status.into(),
                 cycles: t.cycles.map(Into::into),
                 time_added_to_pool: t.time_added_to_pool.map(Into::into),
+                fee: t.fee.map(Into::into),
+                min_replace_fee: t.min_replace_fee.map(Into::into),
             },
             ResponseFormatInnerType::Json => TransactionWithStatusResponse {
                 transaction: t
@@ -556,6 +562,8 @@ impl TransactionWithStatusResponse {
                 tx_status: t.tx_status.into(),
                 cycles: t.cycles.map(Into::into),
                 time_added_to_pool: t.time_added_to_pool.map(Into::into),
+                fee: t.fee.map(Into::into),
+                min_replace_fee: t.min_replace_fee.map(Into::into),
             },
         }
     }
@@ -596,8 +604,8 @@ impl From<tx_pool::TxStatus> for TxStatus {
             tx_pool::TxStatus::Pending => TxStatus::pending(),
             tx_pool::TxStatus::Proposed => TxStatus::proposed(),
             tx_pool::TxStatus::Committed(hash) => TxStatus::committed(hash),
-            tx_pool::TxStatus::Unknown => TxStatus::unknown(),
             tx_pool::TxStatus::Rejected(reason) => TxStatus::rejected(reason),
+            tx_pool::TxStatus::Unknown => TxStatus::unknown(),
         }
     }
 }
diff --git a/util/jsonrpc-types/src/pool.rs b/util/jsonrpc-types/src/pool.rs
index 4a18c73e7c..e13918e857 100644
--- a/util/jsonrpc-types/src/pool.rs
+++ b/util/jsonrpc-types/src/pool.rs
@@ -40,6 +40,11 @@ pub struct TxPoolInfo {
     ///
     /// The unit is Shannons per 1000 bytes transaction serialization size in the block.
     pub min_fee_rate: Uint64,
+    /// RBF rate threshold. The pool reject to replace for transactions which fee rate is below this threshold.
+    /// if min_rbf_rate > min_fee_rate then RBF is enabled on the node.
+    ///
+    /// The unit is Shannons per 1000 bytes transaction serialization size in the block.
+    pub min_rbf_rate: Uint64,
     /// Last updated time. This is the Unix timestamp in milliseconds.
     pub last_txs_updated_at: Timestamp,
     /// Limiting transactions to tx_size_limit
@@ -63,6 +68,7 @@ impl From<CoreTxPoolInfo> for TxPoolInfo {
             total_tx_size: (tx_pool_info.total_tx_size as u64).into(),
             total_tx_cycles: tx_pool_info.total_tx_cycles.into(),
             min_fee_rate: tx_pool_info.min_fee_rate.as_u64().into(),
+            min_rbf_rate: tx_pool_info.min_rbf_rate.as_u64().into(),
             last_txs_updated_at: tx_pool_info.last_txs_updated_at.into(),
             tx_size_limit: tx_pool_info.tx_size_limit.into(),
             max_tx_pool_size: tx_pool_info.max_tx_pool_size.into(),
@@ -241,6 +247,9 @@ pub enum PoolTransactionReject {
 
     /// Transaction expired
     Expiry(String),
+
+    /// RBF rejected
+    RBFRejected(String),
 }
 
 impl From<Reject> for PoolTransactionReject {
@@ -260,6 +269,7 @@ impl From<Reject> for PoolTransactionReject {
             Reject::Resolve(_) => Self::Resolve(format!("{reject}")),
             Reject::Verification(_) => Self::Verification(format!("{reject}")),
             Reject::Expiry(_) => Self::Expiry(format!("{reject}")),
+            Reject::RBFRejected(_) => Self::RBFRejected(format!("{reject}")),
         }
     }
 }
diff --git a/util/launcher/src/shared_builder.rs b/util/launcher/src/shared_builder.rs
index 96d750a198..e1ad368a24 100644
--- a/util/launcher/src/shared_builder.rs
+++ b/util/launcher/src/shared_builder.rs
@@ -463,7 +463,7 @@ fn register_tx_pool_callback(tx_pool_builder: &mut TxPoolServiceBuilder, notify:
 
             let tx_hash = entry.transaction().hash();
             // record recent reject
-            if matches!(reject, Reject::Resolve(..)) {
+            if matches!(reject, Reject::Resolve(..) | Reject::RBFRejected(..)) {
                 if let Some(ref mut recent_reject) = tx_pool.recent_reject {
                     if let Err(e) = recent_reject.put(&tx_hash, reject.clone()) {
                         error!("record recent_reject failed {} {} {}", tx_hash, reject, e);
diff --git a/util/types/src/core/tx_pool.rs b/util/types/src/core/tx_pool.rs
index 43fcd7e547..53baefbf72 100644
--- a/util/types/src/core/tx_pool.rs
+++ b/util/types/src/core/tx_pool.rs
@@ -52,6 +52,10 @@ pub enum Reject {
     /// Expired
     #[error("Expiry transaction, timestamp {0}")]
     Expiry(u64),
+
+    /// RBF rejected
+    #[error("RBF rejected: {0}")]
+    RBFRejected(String),
 }
 
 fn is_malformed_from_verification(error: &Error) -> bool {
@@ -165,33 +169,28 @@ pub struct TransactionWithStatus {
     pub tx_status: TxStatus,
     /// The transaction verification consumed cycles
     pub cycles: Option<core::Cycle>,
+    /// The transaction fee of the transaction
+    pub fee: Option<Capacity>,
+    /// The minimal fee required to replace this transaction
+    pub min_replace_fee: Option<Capacity>,
     /// If the transaction is in tx-pool, `time_added_to_pool` represent when it enter the tx-pool. unit: Millisecond
     pub time_added_to_pool: Option<u64>,
 }
 
 impl TransactionWithStatus {
-    /// Build with pending status
-    pub fn with_pending(
+    /// Build with tx status
+    pub fn with_status(
         tx: Option<core::TransactionView>,
         cycles: core::Cycle,
         time_added_to_pool: u64,
+        tx_status: TxStatus,
+        fee: Option<Capacity>,
+        min_replace_fee: Option<Capacity>,
     ) -> Self {
         Self {
-            tx_status: TxStatus::Pending,
-            transaction: tx,
-            cycles: Some(cycles),
-            time_added_to_pool: Some(time_added_to_pool),
-        }
-    }
-
-    /// Build with proposed status
-    pub fn with_proposed(
-        tx: Option<core::TransactionView>,
-        cycles: core::Cycle,
-        time_added_to_pool: u64,
-    ) -> Self {
-        Self {
-            tx_status: TxStatus::Proposed,
+            tx_status,
+            fee,
+            min_replace_fee,
             transaction: tx,
             cycles: Some(cycles),
             time_added_to_pool: Some(time_added_to_pool),
@@ -203,11 +202,14 @@ impl TransactionWithStatus {
         tx: Option<core::TransactionView>,
         hash: H256,
         cycles: Option<core::Cycle>,
+        fee: Option<Capacity>,
     ) -> Self {
         Self {
             tx_status: TxStatus::Committed(hash),
             transaction: tx,
             cycles,
+            fee,
+            min_replace_fee: None,
             time_added_to_pool: None,
         }
     }
@@ -218,6 +220,8 @@ impl TransactionWithStatus {
             tx_status: TxStatus::Rejected(reason),
             transaction: None,
             cycles: None,
+            fee: None,
+            min_replace_fee: None,
             time_added_to_pool: None,
         }
     }
@@ -228,6 +232,8 @@ impl TransactionWithStatus {
             tx_status: TxStatus::Unknown,
             transaction: None,
             cycles: None,
+            fee: None,
+            min_replace_fee: None,
             time_added_to_pool: None,
         }
     }
@@ -238,6 +244,8 @@ impl TransactionWithStatus {
             tx_status,
             transaction: None,
             cycles,
+            fee: None,
+            min_replace_fee: None,
             time_added_to_pool: None,
         }
     }
@@ -315,6 +323,13 @@ pub struct TxPoolInfo {
     ///
     /// The unit is Shannons per 1000 bytes transaction serialization size in the block.
     pub min_fee_rate: FeeRate,
+
+    /// Min RBF rate threshold. The pool reject RBF transactions which fee rate is below this threshold.
+    /// if min_rbf_rate > min_fee_rate then RBF is enabled on the node.
+    ///
+    /// The unit is Shannons per 1000 bytes transaction serialization size in the block.
+    pub min_rbf_rate: FeeRate,
+
     /// Last updated time. This is the Unix timestamp in milliseconds.
     pub last_txs_updated_at: u64,
     /// Limiting transactions to tx_size_limit


Test patch:
diff --git a/test/src/main.rs b/test/src/main.rs
index 02e09c809b..81da1d8a27 100644
--- a/test/src/main.rs
+++ b/test/src/main.rs
@@ -458,7 +458,16 @@ fn all_specs() -> Vec<Box<dyn Spec>> {
         Box::new(RelayWithWrongTx::new()),
         Box::new(TxsRelayOrder),
         Box::new(SendTxChain),
-        Box::new(DifferentTxsWithSameInput),
+        Box::new(DifferentTxsWithSameInputWithOutRBF),
+        Box::new(RbfEnable),
+        Box::new(RbfBasic),
+        Box::new(RbfSameInput),
+        Box::new(RbfOnlyForResolveDead),
+        Box::new(RbfSameInputwithLessFee),
+        Box::new(RbfTooManyDescendants),
+        Box::new(RbfContainNewTx),
+        Box::new(RbfContainInvalidInput),
+        Box::new(RbfRejectReplaceProposed),
         Box::new(CompactBlockEmpty),
         Box::new(CompactBlockEmptyParentUnknown),
         Box::new(CompactBlockPrefilled),
diff --git a/test/src/specs/tx_pool/descendant.rs b/test/src/specs/tx_pool/descendant.rs
index 04b5a5bc4b..ed23bb7db3 100644
--- a/test/src/specs/tx_pool/descendant.rs
+++ b/test/src/specs/tx_pool/descendant.rs
@@ -1,3 +1,5 @@
+use ckb_jsonrpc_types::Status;
+
 use crate::specs::tx_pool::utils::prepare_tx_family;
 use crate::utils::{blank, commit, propose};
 use crate::{Node, Spec};
@@ -166,21 +168,30 @@ impl Spec for SubmitTransactionWhenItsParentInProposed {
 
         // 1. Propose `tx_family.a` into proposed-pool.
         let family = prepare_tx_family(node);
-        node.submit_transaction(family.a());
-        node.submit_block(&propose(node, &[family.a()]));
+        let tx_a = family.a();
+        node.submit_transaction(tx_a);
+        node.submit_block(&propose(node, &[tx_a]));
         (0..=window.closest()).for_each(|_| {
             node.submit_block(&blank(node));
         });
 
+        // tx_a should in Proposed status
+        let tx_a_status = node.get_transaction(tx_a.hash());
+        assert_eq!(tx_a_status.status, Status::Proposed);
+
         // 2. Submit `tx_family.b` into pending-pool. Then we expect that miner propose it.
         node.submit_transaction(family.b());
         let block = node.new_block_with_blocking(|template| template.proposals.is_empty());
+        let union_proposal_ids = block.union_proposal_ids();
         assert!(
-            block
-                .union_proposal_ids()
-                .contains(&family.b().proposal_short_id()),
+            union_proposal_ids.contains(&family.b().proposal_short_id()),
             "Miner should propose tx_family.b since it has never been proposed, actual: {:?}",
-            block.union_proposal_ids(),
+            union_proposal_ids,
+        );
+        assert!(
+            !union_proposal_ids.contains(&tx_a.proposal_short_id()),
+            "Miner should not propose tx_family.a since it has been proposed, actual: {:?}",
+            union_proposal_ids,
         );
         node.submit_block(&block);
     }
diff --git a/test/src/specs/tx_pool/different_txs_with_same_input.rs b/test/src/specs/tx_pool/different_txs_with_same_input.rs
index a816bd2eb9..f590f7ae81 100644
--- a/test/src/specs/tx_pool/different_txs_with_same_input.rs
+++ b/test/src/specs/tx_pool/different_txs_with_same_input.rs
@@ -7,9 +7,9 @@ use ckb_types::{
     prelude::*,
 };
 
-pub struct DifferentTxsWithSameInput;
+pub struct DifferentTxsWithSameInputWithOutRBF;
 
-impl Spec for DifferentTxsWithSameInput {
+impl Spec for DifferentTxsWithSameInputWithOutRBF {
     fn run(&self, nodes: &mut Vec<Node>) {
         let node0 = &nodes[0];
 
@@ -19,6 +19,7 @@ impl Spec for DifferentTxsWithSameInput {
         info!("Generate 2 txs with same input");
         let tx1 = node0.new_transaction(tx_hash_0.clone());
         let tx2_temp = node0.new_transaction(tx_hash_0);
+
         // Set tx2 fee to a higher value, tx1 capacity is 100, set tx2 capacity to 80 for +20 fee.
         let output = CellOutputBuilder::default()
             .capacity(capacity_bytes!(80).pack())
@@ -46,7 +47,7 @@ impl Spec for DifferentTxsWithSameInput {
             .map(TransactionView::hash)
             .collect();
 
-        // RBF (Replace-By-Fees) is not implemented
+        // RBF (Replace-By-Fees) is not enabled
         assert!(commit_txs_hash.contains(&tx1.hash()));
         assert!(!commit_txs_hash.contains(&tx2.hash()));
 
diff --git a/test/src/specs/tx_pool/mod.rs b/test/src/specs/tx_pool/mod.rs
index bd8ffd3a87..925b5618fc 100644
--- a/test/src/specs/tx_pool/mod.rs
+++ b/test/src/specs/tx_pool/mod.rs
@@ -15,6 +15,7 @@ mod pool_resurrect;
 mod proposal_expire_rule;
 mod remove_tx;
 mod reorg_proposals;
+mod replace;
 mod send_defected_binary;
 mod send_large_cycles_tx;
 mod send_low_fee_rate_tx;
@@ -42,6 +43,7 @@ pub use pool_resurrect::*;
 pub use proposal_expire_rule::*;
 pub use remove_tx::*;
 pub use reorg_proposals::*;
+pub use replace::*;
 pub use send_defected_binary::*;
 pub use send_large_cycles_tx::*;
 pub use send_low_fee_rate_tx::*;
diff --git a/test/src/specs/tx_pool/replace.rs b/test/src/specs/tx_pool/replace.rs
new file mode 100644
index 0000000000..90b972a640
--- /dev/null
+++ b/test/src/specs/tx_pool/replace.rs
@@ -0,0 +1,506 @@
+use crate::{Node, Spec};
+use ckb_jsonrpc_types::Status;
+use ckb_logger::info;
+use ckb_types::{
+    core::{capacity_bytes, Capacity, TransactionView},
+    packed::{Byte32, CellInput, CellOutputBuilder, OutPoint},
+    prelude::*,
+};
+
+pub struct RbfEnable;
+impl Spec for RbfEnable {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+        node0.new_block_with_blocking(|template| template.number.value() != 13);
+        let tx_hash_0 = node0.generate_transaction();
+        let tx1 = node0.new_transaction(tx_hash_0);
+
+        let output = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(70).pack())
+            .build();
+
+        let tx1 = tx1.as_advanced_builder().set_outputs(vec![output]).build();
+
+        node0.rpc_client().send_transaction(tx1.data().into());
+        let ret = node0
+            .rpc_client()
+            .get_transaction_with_verbosity(tx1.hash(), 2);
+
+        assert_eq!(ret.min_replace_fee, None);
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(100);
+        config.tx_pool.min_fee_rate = ckb_types::core::FeeRate(100);
+    }
+}
+
+pub struct RbfBasic;
+impl Spec for RbfBasic {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+        node0.new_block_with_blocking(|template| template.number.value() != 13);
+        let tx_hash_0 = node0.generate_transaction();
+        info!("Generate 2 txs with same input");
+        let tx1 = node0.new_transaction(tx_hash_0.clone());
+        let tx2_temp = node0.new_transaction(tx_hash_0);
+
+        // Set tx2 fee to a higher value, tx1 capacity is 100, set tx2 capacity to 80 for +20 fee.
+        let output = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(80).pack())
+            .build();
+
+        let tx2 = tx2_temp
+            .as_advanced_builder()
+            .set_outputs(vec![output])
+            .build();
+
+        node0.rpc_client().send_transaction(tx1.data().into());
+        let ret = node0
+            .rpc_client()
+            .get_transaction_with_verbosity(tx1.hash(), 2);
+        // min_replace_fee is 363
+        assert_eq!(ret.min_replace_fee.unwrap().to_string(), "0x16b");
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_ok(), "tx2 should replace old tx");
+
+        node0.mine_with_blocking(|template| template.proposals.len() != 2);
+        node0.mine_with_blocking(|template| template.number.value() != 14);
+        node0.mine_with_blocking(|template| template.transactions.len() != 2);
+
+        let tip_block = node0.get_tip_block();
+        let commit_txs_hash: Vec<_> = tip_block
+            .transactions()
+            .iter()
+            .map(TransactionView::hash)
+            .collect();
+
+        // RBF (Replace-By-Fees) is enabled
+        assert!(!commit_txs_hash.contains(&tx1.hash()));
+        assert!(commit_txs_hash.contains(&tx2.hash()));
+
+        // when tx2 should be committed
+        let ret = node0.rpc_client().get_transaction(tx2.hash());
+        assert!(
+            matches!(ret.tx_status.status, Status::Committed),
+            "tx2 should be committed"
+        );
+
+        // verbosity = 1
+        let ret = node0
+            .rpc_client()
+            .get_transaction_with_verbosity(tx1.hash(), 1);
+        assert!(ret.transaction.is_none());
+        assert!(matches!(ret.tx_status.status, Status::Rejected));
+        assert!(ret.tx_status.reason.unwrap().contains("RBFRejected"));
+
+        // verbosity = 2
+        let ret = node0
+            .rpc_client()
+            .get_transaction_with_verbosity(tx2.hash(), 2);
+        assert!(ret.transaction.is_some());
+        assert!(matches!(ret.tx_status.status, Status::Committed));
+
+        let ret = node0
+            .rpc_client()
+            .get_transaction_with_verbosity(tx1.hash(), 2);
+        assert!(ret.transaction.is_none());
+        assert!(matches!(ret.tx_status.status, Status::Rejected));
+        assert!(ret.tx_status.reason.unwrap().contains("RBFRejected"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfSameInput;
+impl Spec for RbfSameInput {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+        node0.new_block_with_blocking(|template| template.number.value() != 13);
+        let tx_hash_0 = node0.generate_transaction();
+        info!("Generate 2 txs with same input");
+        let tx1 = node0.new_transaction(tx_hash_0.clone());
+        let tx2_temp = node0.new_transaction(tx_hash_0);
+
+        let tx2 = tx2_temp.as_advanced_builder().build();
+
+        node0.rpc_client().send_transaction(tx1.data().into());
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfOnlyForResolveDead;
+impl Spec for RbfOnlyForResolveDead {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+        node0.new_block_with_blocking(|template| template.number.value() != 13);
+
+        let tx_hash_0 = node0.generate_transaction();
+
+        let tx1 = node0.new_transaction(tx_hash_0);
+
+        // This is an unknown input
+        let tx_hash_1 = Byte32::zero();
+        let tx2 = tx1
+            .as_advanced_builder()
+            .set_inputs(vec![{
+                CellInput::new_builder()
+                    .previous_output(OutPoint::new(tx_hash_1, 0))
+                    .build()
+            }])
+            .build();
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        let message = res.err().unwrap().to_string();
+        assert!(message.contains("TransactionFailedToResolve: Resolve failed Unknown"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfSameInputwithLessFee;
+
+// RBF Rule #3, #4
+impl Spec for RbfSameInputwithLessFee {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+        node0.new_block_with_blocking(|template| template.number.value() != 13);
+        let tx_hash_0 = node0.generate_transaction();
+        info!("Generate 2 txs with same input");
+        let tx1 = node0.new_transaction(tx_hash_0.clone());
+        let tx2_temp = node0.new_transaction(tx_hash_0);
+
+        let output1 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(80).pack())
+            .build();
+
+        let tx1 = tx1.as_advanced_builder().set_outputs(vec![output1]).build();
+
+        // Set tx2 fee to a lower value
+        let output2 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(90).pack())
+            .build();
+
+        let tx2 = tx2_temp
+            .as_advanced_builder()
+            .set_outputs(vec![output2])
+            .build();
+
+        node0.rpc_client().send_transaction(tx1.data().into());
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+        let message = res.err().unwrap().to_string();
+        assert!(message.contains(
+            "Tx's current fee is 1000000000, expect it to >= 2000000363 to replace old txs"
+        ));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfTooManyDescendants;
+
+// RBF Rule #5
+impl Spec for RbfTooManyDescendants {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+
+        // build txs chain
+        let tx0 = node0.new_transaction_spend_tip_cellbase();
+        let tx0_temp = tx0.clone();
+        let mut txs = vec![tx0];
+        let max_count = 101;
+        while txs.len() <= max_count {
+            let parent = txs.last().unwrap();
+            let child = parent
+                .as_advanced_builder()
+                .set_inputs(vec![{
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(parent.hash(), 0))
+                        .build()
+                }])
+                .set_outputs(vec![parent.output(0).unwrap()])
+                .build();
+            txs.push(child);
+        }
+        assert_eq!(txs.len(), max_count + 1);
+        // send tx chain
+        for tx in txs[..=max_count - 1].iter() {
+            let ret = node0.rpc_client().send_transaction_result(tx.data().into());
+            assert!(ret.is_ok());
+        }
+
+        // Set tx2 fee to a higher value
+        let output2 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(70).pack())
+            .build();
+
+        let tx2 = tx0_temp
+            .as_advanced_builder()
+            .set_outputs(vec![output2])
+            .build();
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+        assert!(res
+            .err()
+            .unwrap()
+            .to_string()
+            .contains("Tx conflict too many txs"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfContainNewTx;
+
+// RBF Rule #2
+impl Spec for RbfContainNewTx {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+
+        // build txs chain
+        let tx0 = node0.new_transaction_spend_tip_cellbase();
+        let mut txs = vec![tx0];
+        let max_count = 5;
+        while txs.len() <= max_count {
+            let parent = txs.last().unwrap();
+            let child = parent
+                .as_advanced_builder()
+                .set_inputs(vec![{
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(parent.hash(), 0))
+                        .build()
+                }])
+                .set_outputs(vec![parent.output(0).unwrap()])
+                .build();
+            txs.push(child);
+        }
+        assert_eq!(txs.len(), max_count + 1);
+        // send tx chain
+        for tx in txs[..=max_count - 1].iter() {
+            let ret = node0.rpc_client().send_transaction_result(tx.data().into());
+            assert!(ret.is_ok());
+        }
+
+        let clone_tx = txs[2].clone();
+        // Set tx2 fee to a higher value
+        let output2 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(70).pack())
+            .build();
+
+        let tx2 = clone_tx
+            .as_advanced_builder()
+            .set_inputs(vec![
+                {
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(txs[1].hash(), 0))
+                        .build()
+                },
+                {
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(txs[4].hash(), 0))
+                        .build()
+                },
+            ])
+            .set_outputs(vec![output2])
+            .build();
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+        assert!(res
+            .err()
+            .unwrap()
+            .to_string()
+            .contains("new Tx contains unconfirmed inputs"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfContainInvalidInput;
+
+// RBF Rule #2
+impl Spec for RbfContainInvalidInput {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+
+        // build txs chain
+        let tx0 = node0.new_transaction_spend_tip_cellbase();
+        let mut txs = vec![tx0];
+        let max_count = 5;
+        while txs.len() <= max_count {
+            let parent = txs.last().unwrap();
+            let child = parent
+                .as_advanced_builder()
+                .set_inputs(vec![{
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(parent.hash(), 0))
+                        .build()
+                }])
+                .set_outputs(vec![parent.output(0).unwrap()])
+                .build();
+            txs.push(child);
+        }
+        assert_eq!(txs.len(), max_count + 1);
+        // send Tx chain
+        for tx in txs[..=max_count - 1].iter() {
+            let ret = node0.rpc_client().send_transaction_result(tx.data().into());
+            assert!(ret.is_ok());
+        }
+
+        let clone_tx = txs[2].clone();
+        // Set tx2 fee to a higher value
+        let output2 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(70).pack())
+            .build();
+
+        let tx2 = clone_tx
+            .as_advanced_builder()
+            .set_inputs(vec![
+                {
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(txs[1].hash(), 0))
+                        .build()
+                },
+                {
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(txs[3].hash(), 0))
+                        .build()
+                },
+            ])
+            .set_outputs(vec![output2])
+            .build();
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+        assert!(res
+            .err()
+            .unwrap()
+            .to_string()
+            .contains("new Tx contains inputs in descendants of to be replaced Tx"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
+
+pub struct RbfRejectReplaceProposed;
+
+// RBF Rule #6
+impl Spec for RbfRejectReplaceProposed {
+    fn run(&self, nodes: &mut Vec<Node>) {
+        let node0 = &nodes[0];
+
+        node0.mine_until_out_bootstrap_period();
+
+        // build txs chain
+        let tx0 = node0.new_transaction_spend_tip_cellbase();
+        let mut txs = vec![tx0];
+        let max_count = 5;
+        while txs.len() <= max_count {
+            let parent = txs.last().unwrap();
+            let child = parent
+                .as_advanced_builder()
+                .set_inputs(vec![{
+                    CellInput::new_builder()
+                        .previous_output(OutPoint::new(parent.hash(), 0))
+                        .build()
+                }])
+                .set_outputs(vec![parent.output(0).unwrap()])
+                .build();
+            txs.push(child);
+        }
+        assert_eq!(txs.len(), max_count + 1);
+        // send Tx chain
+        for tx in txs[..=max_count - 1].iter() {
+            let ret = node0.rpc_client().send_transaction_result(tx.data().into());
+            assert!(ret.is_ok());
+        }
+
+        node0.mine_with_blocking(|template| template.proposals.len() != max_count);
+        let ret = node0.rpc_client().get_transaction(txs[2].hash());
+        assert!(
+            matches!(ret.tx_status.status, Status::Pending),
+            "tx1 should be pending"
+        );
+        node0.mine(1);
+        let ret = node0.rpc_client().get_transaction(txs[2].hash());
+        assert!(
+            matches!(ret.tx_status.status, Status::Proposed),
+            "tx1 should be proposed"
+        );
+
+        let clone_tx = txs[2].clone();
+        // Set tx2 fee to a higher value
+        let output2 = CellOutputBuilder::default()
+            .capacity(capacity_bytes!(70).pack())
+            .build();
+
+        let tx2 = clone_tx
+            .as_advanced_builder()
+            .set_outputs(vec![output2])
+            .build();
+
+        let res = node0
+            .rpc_client()
+            .send_transaction_result(tx2.data().into());
+        assert!(res.is_err(), "tx2 should be rejected");
+        assert!(res
+            .err()
+            .unwrap()
+            .to_string()
+            .contains("all conflict Txs should be in Pending status"));
+    }
+
+    fn modify_app_config(&self, config: &mut ckb_app_config::CKBAppConfig) {
+        config.tx_pool.min_rbf_rate = ckb_types::core::FeeRate(1500);
+    }
+}
diff --git a/test/template/ckb.toml b/test/template/ckb.toml
index c722fa1e55..0eea3eb7b1 100644
--- a/test/template/ckb.toml
+++ b/test/template/ckb.toml
@@ -79,6 +79,7 @@ enable_deprecated_rpc = true
 [tx_pool]
 max_tx_pool_size = 180_000_000 # 180mb
 min_fee_rate = 0 # Here fee_rate are calculated directly using size in units of shannons/KB
+min_rbf_rate = 0 # Here rbf_rate are calculated directly using size in units of shannons/KB
 max_tx_verify_cycles = 70_000_000
 max_ancestors_count = 25
 
diff --git a/tx-pool/src/component/tests/entry.rs b/tx-pool/src/component/tests/entry.rs
index 8aa7edf3ff..6ae6708af2 100644
--- a/tx-pool/src/component/tests/entry.rs
+++ b/tx-pool/src/component/tests/entry.rs
@@ -1,7 +1,6 @@
+use crate::component::sort_key::EvictKey;
 use ckb_types::core::{Capacity, FeeRate};
 
-use crate::component::entry::EvictKey;
-
 #[test]
 fn test_min_fee_and_weight_evict() {
     let mut result = vec![(500, 10, 30), (10, 10, 31), (100, 10, 32)]
diff --git a/tx-pool/src/component/tests/score_key.rs b/tx-pool/src/component/tests/score_key.rs
index 09475f3d19..c12cc7426c 100644
--- a/tx-pool/src/component/tests/score_key.rs
+++ b/tx-pool/src/component/tests/score_key.rs
@@ -1,12 +1,11 @@
 use ckb_types::{
     bytes::Bytes,
     core::{Capacity, TransactionBuilder},
-    packed::{CellInput, OutPoint, ProposalShortId},
+    packed::{CellInput, OutPoint},
     prelude::*,
 };
-use std::mem::size_of;
 
-use crate::component::{entry::TxEntry, pool_map::PoolMap, score_key::AncestorsScoreSortKey};
+use crate::component::{entry::TxEntry, pool_map::PoolMap, sort_key::AncestorsScoreSortKey};
 
 const DEFAULT_MAX_ANCESTORS_COUNT: usize = 125;
 
@@ -27,7 +26,6 @@ fn test_min_fee_and_weight() {
         let key = AncestorsScoreSortKey {
             fee: Capacity::shannons(fee),
             weight,
-            id: ProposalShortId::new([0u8; 10]),
             ancestors_fee: Capacity::shannons(ancestors_fee),
             ancestors_weight,
         };
@@ -51,7 +49,7 @@ fn test_min_fee_and_weight() {
 
 #[test]
 fn test_ancestors_sorted_key_order() {
-    let mut keys = vec![
+    let table = vec![
         (0, 0, 0, 0),
         (1, 0, 1, 0),
         (500, 10, 1000, 30),
@@ -62,33 +60,39 @@ fn test_ancestors_sorted_key_order() {
         (std::u64::MAX, 0, std::u64::MAX, 0),
         (std::u64::MAX, 100, std::u64::MAX, 2000),
         (std::u64::MAX, std::u64::MAX, std::u64::MAX, std::u64::MAX),
-    ]
-    .into_iter()
-    .enumerate()
-    .map(|(i, (fee, weight, ancestors_fee, ancestors_weight))| {
-        let mut id = [0u8; 10];
-        id[..size_of::<u32>()].copy_from_slice(&(i as u32).to_be_bytes());
-        AncestorsScoreSortKey {
-            fee: Capacity::shannons(fee),
-            weight,
-            id: ProposalShortId::new(id),
-            ancestors_fee: Capacity::shannons(ancestors_fee),
-            ancestors_weight,
-        }
-    })
-    .collect::<Vec<_>>();
+    ];
+    let mut keys = table
+        .clone()
+        .into_iter()
+        .enumerate()
+        .map(
+            |(_i, (fee, weight, ancestors_fee, ancestors_weight))| AncestorsScoreSortKey {
+                fee: Capacity::shannons(fee),
+                weight,
+                ancestors_fee: Capacity::shannons(ancestors_fee),
+                ancestors_weight,
+            },
+        )
+        .collect::<Vec<_>>();
     keys.sort();
-    assert_eq!(
-        keys.into_iter().map(|k| k.id).collect::<Vec<_>>(),
-        [0, 3, 5, 9, 2, 4, 6, 8, 1, 7]
-            .iter()
-            .map(|&i| {
-                let mut id = [0u8; 10];
-                id[..size_of::<u32>()].copy_from_slice(&(i as u32).to_be_bytes());
-                ProposalShortId::new(id)
-            })
-            .collect::<Vec<_>>()
-    );
+    let now = keys
+        .into_iter()
+        .map(|k| (k.fee, k.weight, k.ancestors_fee, k.ancestors_weight))
+        .collect::<Vec<_>>();
+    let expect = [0, 3, 5, 9, 2, 4, 6, 8, 1, 7]
+        .iter()
+        .map(|&i| {
+            let key = table[i as usize];
+            (
+                Capacity::shannons(key.0),
+                key.1,
+                Capacity::shannons(key.2),
+                key.3,
+            )
+        })
+        .collect::<Vec<_>>();
+
+    assert_eq!(now, expect);
 }
 
 #[test]