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; at least one node in each first-type blockchain network is managed by a designated manager, and at least one node in the second-type blockchain network is managed by the designated manager; 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 a node managed by the designated manager in the second-type blockchain network broadcasts a second-type blockchain transaction comprising a transaction hash of the first-type blockchain transaction and a network identifier of the first-type blockchain network, to the second-type blockchain network, so as to write the second-type blockchain transaction into a blockchain of the second-type blockchain network; the method for reading data comprises: receiving, by a node managed by the designated manager 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 the 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; and reading a first-type blockchain transaction corresponding to the first-type transaction hash from a blockchain of a first-type blockchain network corresponding to the read network identifier, and returning the 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; at least one node in each first-type blockchain network is managed by a designated manager, and at least one node in the second-type blockchain network is managed by the designated manager; 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 a node managed by the designated manager in the second-type blockchain network broadcasts a second-type blockchain transaction comprising a transaction hash of the first-type blockchain transaction and a network identifier of the first-type blockchain network, to the second-type blockchain network, so as to write the second-type blockchain transaction into a blockchain of the second-type blockchain network; the method for reading data comprises: receiving, by a node managed by the designated manager 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 the 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; and reading a first-type blockchain transaction corresponding to the first-type transaction hash from a blockchain of a first-type blockchain network corresponding to the read network identifier, and returning the first-type blockchain transaction to the user. receiving, by a node managed by the designated manager 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 the 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; and reading a first-type blockchain transaction corresponding to the first-type transaction hash from a blockchain of a first-type blockchain network corresponding to the read network identifier, and returning the first-type blockchain transaction to the user.