The present disclosure provides a cross-blockchain data access method, apparatus and system, and a computer readable medium. The method comprises: sending an authorizing blockchain apparatus a block data request carrying a requesting blockchain apparatus identifier and authorization information, so that the authorizing blockchain apparatus verifies whether the authorization information corresponding to locally-stored requesting blockchain apparatus identifier is matched with the authorization information in the block data request; receiving block data sent by the authorizing blockchain apparatus and corresponding to the block data request, the block data being sent after the authorizing blockchain apparatus verifies that the authorization information corresponding to locally-stored requesting blockchain apparatus identifier is matched with the authorization information in the block data request. According to the present disclosure, through an authorization mechanism, namely, the authorizing blockchain apparatus's authorization for the requesting blockchain apparatus, the requesting blockchain apparatus may be enabled to access the block data of the authorizing blockchain apparatus according to the authorization information, thereby finally achieving cross-blockchain data access. The cross-blockchain data access according to the present disclosure does not require manual participation and exhibits a higher access efficiency.