A data transmission method includes receiving, by a user plane function entity, a data packet from a first terminal through an uplink path corresponding to the first terminal, where the data packet carries addressing information of a second terminal; determining, by the user plane function entity based on information about the uplink path corresponding to the first terminal and the addressing information of the second terminal, a downlink path corresponding to the second terminal; and sending, by the user plane function entity, the data packet to the second terminal through the downlink path corresponding to the second terminal.