A data transmission method and related devices. The method includes: handing over a first terminal device from a second terminal device to a network device; receiving, by the first terminal device, a first packet data convergence protocol (PDCP) data packet sent by the network device; and if the first PDCP data packet is a target PDCP data packet, submitting, by the first terminal device, a second PDCP data packet, where the target PDCP data packet is a PDCP data packet sent by the network device based on a transmission status report, and the transmission status report is a status report sent by the first terminal device or the second terminal device to the network device.