A blockchain-based secure transaction method, the blockchain-based secure transaction method comprising: S1, writing, by a supervisor, a digital certificate into an intelligent contract of a blockchain corresponding to an asset type to be supervised, so that a plurality of institutions with asset accounts under the asset type can obtain a first public key of the supervisor through the digital certificate; S2, providing public-private key pairs for each of the asset accounts of each of the plurality of institutions, based on each of the plurality of public-private key pairs, a predetermined key exchange protocol and the first public key, generating a corresponding additive homomorphic key for each of the asset accounts according to the key exchange protocol, encrypting a balance of each of the asset accounts by using the correspondingly generated additive homomorphic key, and broadcasting each of the encrypted balances to an intelligent contract corresponding to each of a plurality of nodes of the blockchain through the intelligent contract of the blockchain, by institution equipment of each of the corresponding institutions; S3, when an institution of the plurality of institutions initiates a transaction, encrypting a balance of a new account of a transactor for transaction through an additive homomorphic key, and broadcasting the encrypted balance of the new account to each of the intelligent contracts corresponding to each of the plurality of nodes of the blockchain through the intelligent contract of the blockchain, by the institution equipment; and S4, when checking the balance of the new account of the transactor, obtaining a public key corresponding to the new account from the public-private key pairs, generating an additive homomorphic key according to the key exchange protocol based on a supervision private key corresponding to the supervisor and the predetermined key exchange protocol and the obtained public key, and decrypting the encrypted balance of the new account by using the generated additive homomorphic key, by the supervisor. S1, writing, by a supervisor, a digital certificate into an intelligent contract of a blockchain corresponding to an asset type to be supervised, so that a plurality of institutions with asset accounts under the asset type can obtain a first public key of the supervisor through the digital certificate; S2, providing public-private key pairs for each of the asset accounts of each of the plurality of institutions, based on each of the plurality of public-private key pairs, a predetermined key exchange protocol and the first public key, generating a corresponding additive homomorphic key for each of the asset accounts according to the key exchange protocol, encrypting a balance of each of the asset accounts by using the correspondingly generated additive homomorphic key, and broadcasting each of the encrypted balances to an intelligent contract corresponding to each of a plurality of nodes of the blockchain through the intelligent contract of the blockchain, by institution equipment of each of the corresponding institutions; S3, when an institution of the plurality of institutions initiates a transaction, encrypting a balance of a new account of a transactor for transaction through an additive homomorphic key, and broadcasting the encrypted balance of the new account to each of the intelligent contracts corresponding to each of the plurality of nodes of the blockchain through the intelligent contract of the blockchain, by the institution equipment; and S4, when checking the balance of the new account of the transactor, obtaining a public key corresponding to the new account from the public-private key pairs, generating an additive homomorphic key according to the key exchange protocol based on a supervision private key corresponding to the supervisor and the predetermined key exchange protocol and the obtained public key, and decrypting the encrypted balance of the new account by using the generated additive homomorphic key, by the supervisor.