IEEE 802.16 (WiMAX) has been seen as a promising technique for future mesh networks to provide broadband wireless access. Meanwhile, its security is becoming a critical issue with the proliferation of wireless threats in current IEEE 802.11 systems. Though incorporating some security methods in conventional one-hop networks, IEEE 802.16 is still vulnerable to malicious attacks in multihop environments such as mesh networks. In this paper, we analyze the security of IEEE 802.16 standard in its Mesh mode, point out some security holes, and propose some solutions to deal with attacks to IEEE 802.16 mesh networks.