A method for multi-access authentication in Next Generation Network, NGN, a network side authentication center and an access node being provided at a network side, and the access node comprising an access forwarding functional module and an access managing functional module; characterized in that the method comprises: preconfiguring a same key generation algorithm in a user terminal, the access managing functional module, and the network side authentication center; receiving (110, 210, 310, 410, 510, 610, 710),, by the network side authentication center, user terminal information sent by the user terminal via the access node; wherein the user terminal information comprises subscription information of the user terminal and multi-access information of a multi-access service supported by the user terminal, wherein the multi-access information comprises an identifier of the multi-access service and information of multiple interfaces of the user terminal; generating, by the network side authentication center, an authentication vector using a preset algorithm for calculating the authentication vector according to user subscription information reported by the user terminal and identifier information of the user terminal; receiving (120, 220), 320, 420, 520, 620, 720), by the user terminal, an authentication request comprising authentication information sent by the network side authentication center, wherein the authentication information comprises a challenge value; performing, by the user terminal, authentication on the network side according to the authentication information in the authentication request; generating, by the user terminal, keying material and network side authentication information according to the multi-access information of the user terminal itself upon successful authentication, and sending (130, 230, 330, 430, 530, 630, 730) the network side authentication information to the network side authentication center; performing, by the network side authentication center, authentication on the network side authentication information using the authentication vector; and generating, by the network side authentication center, keying material according to the multi-access information of the user terminal upon successful authentication, wherein the user terminal and the authentication server generate the keying material based on a same element and the same key generation algorithm. preconfiguring a same key generation algorithm in a user terminal, the access managing functional module, and the network side authentication center; receiving (110, 210, 310, 410, 510, 610, 710),, by the network side authentication center, user terminal information sent by the user terminal via the access node; wherein the user terminal information comprises subscription information of the user terminal and multi-access information of a multi-access service supported by the user terminal, wherein the multi-access information comprises an identifier of the multi-access service and information of multiple interfaces of the user terminal; generating, by the network side authentication center, an authentication vector using a preset algorithm for calculating the authentication vector according to user subscription information reported by the user terminal and identifier information of the user terminal; receiving (120, 220), 320, 420, 520, 620, 720), by the user terminal, an authentication request comprising authentication information sent by the network side authentication center, wherein the authentication information comprises a challenge value; performing, by the user terminal, authentication on the network side according to the authentication information in the authentication request; generating, by the user terminal, keying material and network side authentication information according to the multi-access information of the user terminal itself upon successful authentication, and sending (130, 230, 330, 430, 530, 630, 730) the network side authentication information to the network side authentication center; performing, by the network side authentication center, authentication on the network side authentication information using the authentication vector; and generating, by the network side authentication center, keying material according to the multi-access information of the user terminal upon successful authentication, wherein the user terminal and the authentication server generate the keying material based on a same element and the same key generation algorithm.