With the aim at solving the problem of a selfish node refusing forward service requests of a mobile Ad hoc network, based on a Game theory in economics, this paper describes the method of identifying selfish nodes through detecting the cooperation rates of neighboring nodes and proposes statistics based on repeated Game strategies LTFT and LEpTFT. Also, the paper proposes a rule of adopting different strategies according to different aims of cooperation. Analysis shows that the strategies and rule can effectively encourage cooperation and punish selfishness to solve network problem and nodes to benefit from tradeoffs.