Disclosed are a data processing method and apparatus for a blockchain, and a medium. The data processing method for the blockchain is applied to a blockchain node. The method includes: obtaining a transaction request for creating a synchronizing group; based on the transaction request for creating the synchronizing group, determining one or more sequential blocks from a first block to a current block as one or more synchronizing blocks of the synchronizing group; determining a synchronizing signature of the synchronizing group based on the one or more synchronizing blocks; and recording the synchronizing signature as transaction data in the current block.