Embodiments of the present invention disclose a terminal authenticating method, including: receiving, by a UE-to-network relay UE-R, a first request message sent by user equipment UE; sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE; receiving, by the UE-R, an authentication request message sent by the control network element, and determining whether the authentication request message is for authenticating on the UE; if the authentication request message is for authenticating on the UE, sending, by the UE-R, an authentication request message to the UE; and receiving, by the UE-R, an authentication response message sent by the UE according to the authentication request message, and sending the authentication response message to the control network element.