Wireless mesh sensor network (WMSN) merges advantages of wireless mesh networks and wireless sensor networks, especially on scalability, robustness and balanced energy dissipation. Routing in WMSNs faces with more challenges than that in traditional sensor networks on account of multiple sink nodes and the mobility of nodes. This paper focuses on two challenging problems. Firstly, we propose a reliable architecture of WMSNs by deploying multiple mobile mesh nodes in each sensor network to collect sensed data, which improves the scalability and performance of WMSNs. Also, we design a routing protocol characteristic to WMSNs. The routing protocol aims at maximizing the lifetime of sensor networks by reducing total energy consumption of a sensor network, as well as balancing energy usage among sensor nodes.