A data transmission method includes obtaining dequeue information that indicates a queue which requests to output data in a communications device and a target data volume that is output from each queue at a time, and the communications device manages the target data volume based on a burst value, reading, based on the queue, a sub-packet descriptor (PD) that is obtained by segmenting the first PD, the sub-PD includes target description information indicating a target data packet, the first PD includes first description information indicating a first data packet set including the target data packet, the first data packet set and the sub-PD are stored in a packet cache including a dynamic random access memory (DRAM), the first PD is stored in a control cache including a static random access memory (SRAM), and determining, the target data packet based on the sub-PD, and sending the target data packet.