A data transmission method implemented by a network device, where the data transmission method includes receiving a first data packet sent by a transmit end, buffering the first data packet to a low-priority queue when the first data packet is sent by the transmit end during a first round-trip time (RTT) of a data transmission phase between the transmit end and a receive end, receiving a second data packet from the transmit end, buffering the second data packet to a high-priority queue when the second data packet is not sent by the transmit end during the first RTT, and forwarding the second data packet in the high-priority queue before the first data packet in the low-priority queue.