In order to improve the energy balance of wireless sensors network, we present a Leach-based routing protocol using Optimized Energy Welfare (OEW) called Leach-OEW. The concept of OEW is raised based on the optimized social welfare. The OEW is applied to the election of the cluster heads in the Leach routing protocol of wireless sensors networks to achieve energy balance as well as energy efficiency. The simulation results show that the improved Leach protocol balances the energy consumption of sensor nodes, prolongs the life time of network compared with the Leach and PARPEW protocol.