Abstract: Characteristics of underwater acoustic sensor networks make it a remarkable property of the routing protocol to efficiently utilize network node energy and extend network lifespan.In this paper,a routing protocol with extended network lifespan is proposed based on the protocol of Destination Sequenced Distance Vector(DSDV) and a routing protocol with minimizing-cost field.The proposed protocol keeps balance of every node′s energy consumption to extend network lifespan.Simulation results show that the proposed protocol may prolong network lifespan by 10% with respect to DSDV.