Since the WiMAX mesh network can guarantee the QoS, it is possible to be deployed as backhaul network. And we need to consider the scheduling efficiency, throughput and robustness for it. In this paper, we analyze the scheduling mechanism of the WiMAX mesh network and point out the problem of current backhaul network structure. We proposed a new WiMAX mesh network structure with multiple BS as egress, and propose an efficient optimal scheduling algorithm for this new network structure. The detailed procedure for deploying this algorithm is described as well. We developed a simulation platform to verify this algorithm in WiMAX mesh network with 20 and 50 MESH SS nodes respectively. The simulation result shows that our algorithm improves the efficiency varying from 53 percent to 70 percent. We also illustrate that our scheduling algorithm can solve the bottleneck problem of the backhaul network.