Abstract: Disclosed is a method for auto setting security mechanism of WLAN. The method comprises a normal step, which enables a station and an access point to execute the communicating negotiation between them, and a security setting step, which is used to execute the security mechanism setting automatically. Moreover, the security setting step comprises a defining step, which defines a plurality of parameters of the access point and a connecting step, which enables the station to connect to the access point, the access point to broadcast the UDP packages periodically, and sets the WLAN security settings. After the security setting step, the stations and access points execute the normal step again. Another aspect of the present invention is an apparatus for auto setting security mechanism of WLAN.