In an embodiment, the present invention discloses a method for accessing a network by UE, a core network entity, a base station, and first UE. The method includes determining, by a base station, that first UE provides relay for the second UE; and sending, by the base station, a first message including a first identifier to the first UE. The first message is used to manage a data radio bearer DRB of the first UE so that the DRB of the first UE is used to transmit data of the second UE, and the first identifier is in a one-to-one correspondence with the second UE.