Abstract: In this paper, we designed an energy efficient routing protocol for MWSN based on Genetic Algorithm (GA). The clustering process, the power model were elaborated in details, and the optimal residual energy of a node was found by using GA. we did the simulation studies based on OMNet++, and compared with M-LEACH. The results revealed that, the network lifetime, average packet delivery ratio and average end-to-end delay of energy-efficient routing protocol were all superior to M-LEACH. The protocol was more suitable for MWSN.