说明：  The cluster head is selected by the random number generated by nodes in the hierarchical routing protocol which is implementing Low Energy Adaptive Clustering Hierarchy (LEACH). As a result, the cluster head may be chosen randomly and be distributed asymmetrically. Focus on this problem, this paper introduces a function to improve the problem. This function uses the relative distance between nodes and base station and the round number as its parameters. Hence, the distribution of cluster head can be symmetrical through changing parameters of the function, and. With the increasing of running time, every node in the network has the chance to be a cluster head, that is, the energy consumption could be balance. The simulation result shows that the lifetime of Wireless Sensor Network (WSN) has been prolonged about 14 .