Abstract: Considering at the characteristic that the energy of node is limited in wireless sensor networks, an energy-efficiency optimizing model both considering transmission energy consumption and its equilibrium characteristic is build in this paper. To make maximum of the total remaining energy and minimum of the remaining energy variance as optimal objectives, it optimizes energy efficiency of the network by reasonably allocating the flow on multipath. The weigh evaluation function is used to solve this model, and then a Multipath Flow Allocating Routing (MFAR) algorithm is proposed based on it. Simulation results show that, MFAR algorithm can reasonably allocate the flow on multipath, improve the network energy efficiency significantly, and achieve the goal of reducing energy consumption and balancing its distribution simultaneously.