With the constant enlargement of the range of application of wireless sensor network, extending wireless sensor network’ life cycle has attracted more and more attention under the circumstances of limited node energy. On account of three-dimensional space background for the environmental monitoring of high buildings, this thesis put forward an improved energy-saving optimum algorithm of LEACH: improving probability of high-energy node elected as cluster head during cluster head election; selecting a network with the minimum communication cost. The simulation experiment indicates that under the layout of three-dimensional space, improving algorithm makes the load of wireless sensor network more balancing, and extending network’ life cycle. what’ s more, simulation result, in a way, serves as theoretical basis for a further study on the life cycle of wireless sensor network.