A data transmission method includes encapsulating, by a first device, first target data into N remote direct memory access (RDMA) packets according to an RDMA protocol, sequentially sending, by the first device, the N RDMA packets to the second device according to a packet sequence number (PSN) sequence of the N RDMA packets, where each of the N RDMA packets carries a first data write address, and the first data write address is an address for writing data in each of the N RDMA packets into the second device such that the second device directly obtains the first data write address in each RDMA packet from the RDMA packet, and writes the target data into storage space corresponding to the first data write address.