Low-complexity joint power allocation and route planning algorithm for multiple antennas wireless sensor networks (WSN) is introduced in this paper. The Quality-of-Service (QoS) aware packet forwarding problem is cast into the framework of dynamic programming, such that adaptive power allocation can be jointly realized at each hop. State space partition techniques and state aggregation approximation architecture are introduced to derive the value function. In order to reduce the computational complexity, we present a sub-optimal routing protocol by performing the route planing and power allocation separately. Simulation results indicate that the proposed protocols significantly outperform classical routing algorithms.