Abstract: Embodiments of the present invention provide a data transmission method and apparatus, a communications device, and a communications system, which relate to the communications field, and the method includes: receiving at least two IP packets; determining at least two multiplexing packets from the at least two IP packets according to a multiplexing policy; encapsulating the at least two multiplexing packets into one GTP-U packet; and sending the GTP-U packet. In the present invention, at least two IP packets that meet a multiplexing policy are encapsulated into one GTP-U packet, and the GTP-U packet is sent. When an IP packet is being transmitted on a PRN, resources consumed for obtaining a transmission route each time when forwarding is performed are significantly reduced compared with the prior art. In addition, a proportion of an IP packet to a GTP-U packet increases, thereby improving transmission efficiency.