Abstract: In view of problems of high energy consumption and short life time of classical minimum hop count routing algorithm of wireless sensor networks, an improved algorithm was proposed. The improved algorithm sets node delay timer on gradient field establishing stage, and comprehensively considers the effectiveness and balance of the energy consumption of the sensor nodes on the data transmission stage, and dynamically selects the only relay node by the energy cost function to construct the minimum energy consumption path from the source node to the Sink node. The simulation results show that the improved algorithm can further decrease energy consumption of the sensor node, prolong life time of networks, and meet demands of underground wireless sensor networks.