Methods, systems, and apparatus, including computer programs encoded on computer storage media, for parallel-processing blockchain transactions are provided. One of the methods includes: obtaining a plurality of candidate transactions for adding to a blockchain; grouping the candidate transactions into one or more transaction groups; creating one or more copies of at least a portion of a data structure of a latest block of the blockchain; associating the one or more transaction groups respectively with the one or more copies of the data structure; executing the candidate transactions in each of the transaction groups and updating the associated copies of the data structure; and merging the updated copies of the data structure to obtain at least a portion of a new data structure of a new block to add to the blockchain.