The invention provides a method and a system for accessing transaction records of block chains. The method and the system are used for solving a problem that sensitive data may be leaked out in a scene where the block chains are applied in production cooperation since transaction data in a block chain account book is stored in a clear manner in the prior art can be freely accessed. The corresponding method and the corresponding system are provided. The method comprises steps of sending respective private keys of all block chain nodes to a management server for storage; the block chain nodes encrypt the to-be-stored transaction records by use of the respective public keys; when the transaction data needs to be accessed, a research request is given out to the management server; after the relation between a searcher and a searched person is judged, the transaction data is decrypted by use of the private keys and sent to the searcher nodes, thereby achieving data safety of the transactiondata in the block chain account book.