Abstract: This paper uses the viewpoints and methods in game theory to solve the packet forwarding problem in wireless sensor networks.A packet forwarding model is designed for wireless sensor networks,and the node's Pareto optimal utility participating in packet forwarding is analyzed.An algorithm named POUPF(Pareto Optimal Utility based Packet Forwarding) is proposed,which is proved to be able to set a Nash equilibrium and to obtain the Pareto optimal utility for each node.The simulation results verify that POUPF enables the nodes to achieve the Pareto optimal utility by spontaneous cooperation,and the deviation at any one node will decrease the utilities of all related nodes.