A method for reading data based on a plurality of blockchain networks, wherein a data recording system comprises at least two first-type blockchain networks and one second-type blockchain network; wherein, when data to be stored is submitted to any first-type blockchain network, the first-type blockchain network writes a first-type blockchain transaction comprising the data to be stored into a blockchain of the first-type blockchain network, and sends a transaction hash of the first-type blockchain transaction comprising the data to be stored to the second-type blockchain network, so the second-type blockchain network writes a second-type blockchain transaction comprising the transaction hash and a network identifier of the first-type blockchain network into a blockchain of the second-type blockchain network; and the method for reading data comprises: receiving, by a node in the second-type blockchain network, a first-type transaction hash sent by a user, wherein the first-type transaction hash is a transaction hash of a first-type blockchain transaction to be read; in a blockchain of the second-type blockchain network, querying a second-type blockchain transaction comprising the first-type transaction hash, and reading a network identifier from the queried second-type blockchain transaction; sending the first-type transaction hash to a first-type blockchain network corresponding to the read network identifier, and obtaining a transaction corresponding to the first-type transaction hash, wherein the first-type blockchain transaction is returned by the first-type blockchain network; and sending the obtained first-type blockchain transaction to the user. wherein a data recording system comprises at least two first-type blockchain networks and one second-type blockchain network; wherein, when data to be stored is submitted to any first-type blockchain network, the first-type blockchain network writes a first-type blockchain transaction comprising the data to be stored into a blockchain of the first-type blockchain network, and sends a transaction hash of the first-type blockchain transaction comprising the data to be stored to the second-type blockchain network, so the second-type blockchain network writes a second-type blockchain transaction comprising the transaction hash and a network identifier of the first-type blockchain network into a blockchain of the second-type blockchain network; and the method for reading data comprises: receiving, by a node in the second-type blockchain network, a first-type transaction hash sent by a user, wherein the first-type transaction hash is a transaction hash of a first-type blockchain transaction to be read; in a blockchain of the second-type blockchain network, querying a second-type blockchain transaction comprising the first-type transaction hash, and reading a network identifier from the queried second-type blockchain transaction; sending the first-type transaction hash to a first-type blockchain network corresponding to the read network identifier, and obtaining a transaction corresponding to the first-type transaction hash, wherein the first-type blockchain transaction is returned by the first-type blockchain network; and sending the obtained first-type blockchain transaction to the user. receiving, by a node in the second-type blockchain network, a first-type transaction hash sent by a user, wherein the first-type transaction hash is a transaction hash of a first-type blockchain transaction to be read; in a blockchain of the second-type blockchain network, querying a second-type blockchain transaction comprising the first-type transaction hash, and reading a network identifier from the queried second-type blockchain transaction; sending the first-type transaction hash to a first-type blockchain network corresponding to the read network identifier, and obtaining a transaction corresponding to the first-type transaction hash, wherein the first-type blockchain transaction is returned by the first-type blockchain network; and sending the obtained first-type blockchain transaction to the user.