Embodiments of this application provide a data processing method, apparatus, and device, a blockchain system, and a computer-readable storage medium. The method is performed by a computer device acting as a blockchain client of the blockchain system, the method including: transmitting an identity query request to an identity chain node, the identity query request including an identity identifier (ID) of the blockchain client and to-be-processed data; receiving node identity information returned by the identity chain node based on the identity ID and the data; determining, according to the node identity information, a target blockchain node configured to process the data within a blockchain node set; transmitting the data ID to the target blockchain node, to query data on at least one of the plurality of application chains based on the data ID through the target blockchain node; and receiving the queried data returned by the target blockchain node.