A method for a access point device having first network identity information to automatically establish a security link with a peer access point device in a wireless communication system includes searching and receiving a beacon corresponding to the peer access point device by radio frequency scan, obtaining second network identity information corresponding to the peer access point device from the beacon, determining a primary-secondary relationship for the access point device and the peer access point device according to the first and second network identity information, generating or receiving security data according to the primary-secondary relationship, and then establishing the security link with the peer access point device according to the security data.