WiMAX security has two goals, one is to provide privacy across the wireless network and the other is to provide access control to the network. Privacy is accomplished by encrypting connections between the subscriber station and the base station. The base station protects against unauthorized access by enforcing encryption of service flows across the network. This paper presents the main content of WiMAX security, lists the categories of encryption keys in both IEEE 802.16-2004 and IEEE 802.16e-2005 standards, analyzes the principium, encryption process of RSA, DES-CBC, AES-CTR and AES-CCM.