Embodiments of the present application provide a data transmission method and a communications apparatus. A Hypertext Transfer Protocol version 2 HTTP/2 adaptation layer is configured between an application layer and a Multipath Transmission Control Protocol MPTCP layer of a protocol stack. All frames belonging to a same HTTP/2 stream are allocated to a same MPTCP subflow for transmission, so that a data throughput is large, and system robustness is good, thereby improving HTTP/2 stream transmission performance.