WLAN access method, WAG and network fusion system

The invention relates to a WLAN (wireless local area network) access method which comprises the steps that a WAG (WLAN access gateway) establishes an SIP (session initiation protocol) with a terminal through an AC/BAS (access control/broadband access server), and conducts PPP (point-to-point protocol) negotiation with equipment on a core network side of an LTE (long term evolution) network; during the PPP negotiation, the WAG requests authorization for an AAA (against all authority) server on the core network side; when the authorization is successful, the WAG sends a PMIP (proxy mobile internet protocol) request to a PDN GW (packet data network gateway); the WAG receives a PMIP access success message responded by the PDN GW, and sends an IP (internet protocol) address distributed by the PDN GW to the terminal according to the PMIP access success message to accomplish the PPP negotiation; and a user session from the terminal to a service network of the LTE network through the WAG and the PDN GW is established. The invention relates to the WAG and a network fusion system. According to the WLAN access method, the WAG and the network fusion system, effective fusion of service functions of a WLAN and the LTE network is achieved by combining the characteristic of the available network; the available network is improved as less as possible; and an influence on a user is reduced.