A data transmission method and apparatus, and a related device are disclosed. The data transmission method includes: adding, by first UE, a first RBID and/or terminal identifier information of the first UE to data that needs to be sent, where a first RB corresponding to the first RBID is located between the first UE and a network side device, the first RBID is allocated to the first UE by the network side device, the terminal identifier information is a layer 2 identifier of the first UE, the layer 2 identifier is used to instruct an access network to identify the first UE, and the terminal identifier information includes a C-RNTI, an IP address, a TMSI, or an IMSI; and sending, by the first UE, the data to which the first RBID and/or the terminal identifier information is added to second UE.