Due to the limitation of energy, the routing protocols of Wireless Sensor Network (WSN) must minimize energy consumption and thus extend the network lifetime. Low Energy Adaptive Clustering Hierarchy (LEACH) is the first classical hierarchical routing protocol in WSN. A timer is introduced while electing the optimal sensor node as cluster head. During data transmission, the authors are using single hop and multi-hop hybrid routing to communicate with the base station, so that it can utilize energy more effectively and evenly. By analyzing the disadvantage of LEACH algorithm, this paper proposes an improved LEACH algorithm.