The invention discloses a method for implementing EAP authentication in a WLAN. The WLAN comprises a mobile phone terminal bound with an SIM card or a USIM card, a wireless AP, a dedicated AAA server and a dedicated authentication server, wherein the mobile phone terminal is communicated with the wireless AP, the wireless AP is communicated with the dedicated AAA server, the dedicated AAA server is communicated with the dedicated authentication server, and each dedicated AAA user stores the IMSI, encryption algorithms, algorithm identifiers and key information in the dedicated authentication server. According to the method disclosed by the invention, the multi-group EAP-SIM/AKA authentication combination based on mobile phone user identification cards (SIM/USIM cards) adopts other keys and algorithms in the SIM/USIM cards to automatically complete WIFI authentication and login by taking the WIFI authentication of the mobile terminal of the mobile phone as the basis and taking EAP-SIM/AKA as an authentication mode without affecting the authentication keys and algorithms required for the standard authentication command of the SIM/USIM cards, and the characteristics that the operation is simple and convenient and the user can use WIFI without perception can be achieved; and in addition, the traditional HLR or HSS pointing to mobile operators can be avoided, and convenient conditions can be provided for the popularization and promotion of EAP-SIM/AKA.