LEACH (Low Energy Adaptive Clustering Hierarchy) routing protocol is the conventional clustering communication protocol which is widely used in Wireless Sensor Networks. However, in LEACH, the nodes consume their energy quickly and the efficiency of energy deceases because the nodes with low energy and far away from base station become the cluster head nodes. By analyzing the energy model and considering three important factors: The energy of each node, the number of times of nodes that are chosen to be the cluster heads and the distances between nodes and base station, we change the node's threshold function to prolong the network's lifetime and realize the balance of energy in network. The simulation results indicate that the new protocol can prolong network's life time and balance energy consumption of nodes.