Wimax stands for worldwide interoperability for microwave access. Wimax Technology that enables ubiquitous delivery of the wireless broadband service for fixed and/or for mobile users . wimax is wireless digital communication system also known as 802.16 . which is intended for wireless " Metropolitan area networks " .The challenge for Broadband Wireless Access networks is in provides the quality of service (QoS) simultaneously to services with very different characteristics. QoS support in wireless networks is a much more difficult task than in wired networks, mainly because the characteristics of a wireless link are highly variable and unpredictable, both on a time-dependent basis and a location dependent basis. A special requirement for mobile device is ability to change the serving BS ,if there exists another BS , for example better link quality to reach of MS . we consider an interworking architecture of wireless mesh backbone and propose an effective vertical handoff scheme between 802.11 and 802.16 wireless access networks. The proposed reducing handoff signaling overhead on the wireless backbone and providing a low handoff delay to mobile nodes.While handoff a mechanism to maintain uninterrupted user communication session during a user movements from one location to another . Wimax supports for various types off handoff to maintain communication .