A terminal authenticating method, comprising: 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, a first authentication request message sent by the control network element, wherein the first authentication request message comprises an authentication vector that comprises authentication identification information indicating that the authentication is to be performed on the UE, and determining, by the UE-R whether the first authentication request message is for authenticating on the UE based on the authentication identification information; sending, by the UE-R, a second authentication request message to the UE when the first authentication request message is for authenticating on the UE, wherein the second authentication request message sent by the UE-R comprises parameters of the authentication vector that include the authentication identification information; and receiving, by the UE-R, an authentication response message sent by the UE according to the second authentication request message; and sending, by the UE-R, the authentication response message to the control network element, so as to complete authentication on the UE by using the control network element; wherein when the first request message sent by the UE comprises the identification information indicating that authentication is to be performed on the UE, the sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE comprises: adding, by the UE-R to the second request message, the identification information indicating that authentication is to be performed on the UE that is carried in the first request message, and sending the second request message to the control network element; and wherein when the first request message sent by the UE does not comprise the identification information indicating that authentication is to be performed on the UE, the sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE comprises: adding, by the UE-R, the identification information indicating that authentication is to be performed on the UE to the second request message, and sending the second request message to the control network element. 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, a first authentication request message sent by the control network element, wherein the first authentication request message comprises an authentication vector that comprises authentication identification information indicating that the authentication is to be performed on the UE, and determining, by the UE-R whether the first authentication request message is for authenticating on the UE based on the authentication identification information; sending, by the UE-R, a second authentication request message to the UE when the first authentication request message is for authenticating on the UE, wherein the second authentication request message sent by the UE-R comprises parameters of the authentication vector that include the authentication identification information; and receiving, by the UE-R, an authentication response message sent by the UE according to the second authentication request message; and sending, by the UE-R, the authentication response message to the control network element, so as to complete authentication on the UE by using the control network element; wherein when the first request message sent by the UE comprises the identification information indicating that authentication is to be performed on the UE, the sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE comprises: adding, by the UE-R to the second request message, the identification information indicating that authentication is to be performed on the UE that is carried in the first request message, and sending the second request message to the control network element; and wherein when the first request message sent by the UE does not comprise the identification information indicating that authentication is to be performed on the UE, the sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE comprises: adding, by the UE-R to the second request message, the identification information indicating that authentication is to be performed on the UE that is carried in the first request message, and sending the second request message to the control network element; and wherein when the first request message sent by the UE does not comprise the identification information indicating that authentication is to be performed on the UE, the sending, by the UE-R, a second request message to a control network element according to the first request message sent by the UE comprises: adding, by the UE-R, the identification information indicating that authentication is to be performed on the UE to the second request message, and sending the second request message to the control network element.