Abstract: In order to make up the deficiencies of free-riding, tragedy of the commons, fake-file, collusion and non-cooperation of peer to peer (P2P) networks, by analyzing the types of peers and setting the incentive principles, a new P2P incentive mechanism based on electronic coupons combined with a novel global reputation evaluation algorithm was proposed to regulate the behavior of peers. The mechanism utilized the hash chain and Payword technology to design the electronic coupon suitable for the distribution payment in P2P networks and also introduced the punishment factor to realize the peer's reputation evaluation algorithm. To verify the feasibility, the performance and the security of the mechanism, a series of experiments was implemented in the simulation environment. The results of experiment and analysis show that the mechanism can effectively curb the malicious nodes and stimulate peers to offer their resources and cooperation actively and honestly. Moreover, it could promote P2P networks to be harmonious and systematic computing environments able to support task collaboration and resource sharing.