A power control algorithm based on node dynamic clustering is proposed, in order to prolong the network lifetime and solve the problem of limited node energy in wireless sensor networks of high voltage power transmission monitoring. The algorithm is based on the transmission monitoring network architecture. By analyzing the geographical relationship between sensor nodes, considering the residual energy of geographical information and nodes comprehensively, and using cluster analysis method to dynamically cluster nodes that have similarity nature, all packets can forward from one representative node to another node during transmission phase. Meantime, variable-power modulation technology is used for packet transmission. Simulation results show that the algorithm is effective to reduce network energy consumption, and prolong the lifetime of the network.