Abstract: A novel cross-layer communication protocol is proposed and named power controlled directed spanning tree (PCDST), where a directed spanning tree routing algorithm is introduced to solve the problem of unnecessary energy consumption during data transmission and control the transmission power of node so as to moderate the competition intensity in communication network. A network utility maximum (NUM) model is developed to control further the transmission power that is regarded as a key factor. Based on the Prim-dual algorithm, a Lagrange dual function is designed to deduce the optimal solution set of transmission power. Taking advantage of such cross-layer strategies, WSN is enable to keep up smooth communication with energy saving. The simulation results showed that the performance of the proposed protocol is much better in both energy efficiency and improvement of communication throughput.