A method for implementing authentication and accounting in interaction between a wireless local area network, WLAN, and a fixed network, wherein: after user equipment, UE, accesses a network, performing, by a broadband network gateway, BNG, interaction with an authentication authorization accounting server, AAA, and implementing authentication and accounting on the UE in turn through an AAA proxy function of an access controller, AC; wherein performing interaction between the BNG and the AAA and implementing authentication on the UE through the AAA proxy function of the AC comprises: sending, by the BNG, an authentication request message received from the UE to the AC based on an AAA protocol; sending, by the AC, the authentication request message to the AAA based on the AAA protocol after the AC receives the authentication request message; and authenticating, by the AAA, the UE according to the authentication request message; after the authentication succeeds, the method further comprising: replying, by the AAA, an authentication success message to the AC based on the AAA protocol; sending, by the AC to an access point, AP, a key of the UE contained in the received authentication success message and used to inform the AP that the authentication on the UE is successful, and replying, by the AC, an authentication success message to the BNG based on the AAA protocol; negotiating, by the AP, a new key with the UE after receiving the key of the UE; and storing, by the BNG, user information of the UE after receiving the authentication success message; and replying, by the BNG, an authentication success message to the UE; wherein the new key is for encrypting data transmitted by the UE. after user equipment, UE, accesses a network, performing, by a broadband network gateway, BNG, interaction with an authentication authorization accounting server, AAA, and implementing authentication and accounting on the UE in turn through an AAA proxy function of an access controller, AC; wherein performing interaction between the BNG and the AAA and implementing authentication on the UE through the AAA proxy function of the AC comprises: sending, by the BNG, an authentication request message received from the UE to the AC based on an AAA protocol; sending, by the AC, the authentication request message to the AAA based on the AAA protocol after the AC receives the authentication request message; and authenticating, by the AAA, the UE according to the authentication request message; sending, by the BNG, an authentication request message received from the UE to the AC based on an AAA protocol; sending, by the AC, the authentication request message to the AAA based on the AAA protocol after the AC receives the authentication request message; and authenticating, by the AAA, the UE according to the authentication request message; after the authentication succeeds, the method further comprising: replying, by the AAA, an authentication success message to the AC based on the AAA protocol; sending, by the AC to an access point, AP, a key of the UE contained in the received authentication success message and used to inform the AP that the authentication on the UE is successful, and replying, by the AC, an authentication success message to the BNG based on the AAA protocol; negotiating, by the AP, a new key with the UE after receiving the key of the UE; and storing, by the BNG, user information of the UE after receiving the authentication success message; and replying, by the BNG, an authentication success message to the UE; wherein the new key is for encrypting data transmitted by the UE. replying, by the AAA, an authentication success message to the AC based on the AAA protocol; sending, by the AC to an access point, AP, a key of the UE contained in the received authentication success message and used to inform the AP that the authentication on the UE is successful, and replying, by the AC, an authentication success message to the BNG based on the AAA protocol; negotiating, by the AP, a new key with the UE after receiving the key of the UE; and storing, by the BNG, user information of the UE after receiving the authentication success message; and replying, by the BNG, an authentication success message to the UE; wherein the new key is for encrypting data transmitted by the UE.