A data transmission method and apparatus to separate control information and data information in a Transmission Control Protocol (TCP) protocol stack on a concentrator in order to improve data transmission efficiency. The data transmission method includes that a concentrator of a first device generates a first TCP packet based on first data that needs to be sent by a collector of the first device to a second device, where a payload of the first TCP packet is empty, the first TCP packet includes indication information, and the indication information instructs the collector to generate a second TCP packet based on the first TCP packet. The concentrator sends the first TCP packet to the collector. The collector generates the second TCP packet based on the first TCP packet and sends the second TCP packet to the second device.