Wireless Mesh Network (WMN) is an upcoming wireless network technology and is mainly used to provide broadband internet in remote locations. It is characterized by minimum fixed infrastructure requirement and is operated in an open medium, such that any user within the range covered by mesh routers may access the network. So a critical requirement for the security in WMN is the authentication of users. However, WMN is far from mature for large-scale deployment in some applications due to the lack of the satisfactory guarantees on security. A wellperformed security framework for WMN will contribute to network survivability and strongly support the network growth or reduction. A key management model to overcome the scalability issue on security aspect for large-scale deployment of WMN i.e. Worldwide WMN is proposed in this work, which aims to guarantee wellperformed key management services and protection from potential attacks. Here, we use a combination of techniques, such as zonebased topology structure, off-line CA, virtual certification authority ) etc.