Abstract: Because of the nodes inherent rationality,P2P network system will generate the free-riding behavior that will cause the conflict between personal interests and system performance．This kind of behavior will greatly reduce the network efficiency and utility．A set of social norm model applied in P2P networkwas established based on the social norm in combination with the ideology of boycott．This mode can punish the nodes that have violated the social norm and stimulate nodes to select cooperation strategy,generate the condition of the balance of cooperation strategy through game revenue analysis．The results of the simulation experiment show that this model can both promote the node colla-boration effectively and inhibit the free-riding behavior.

Key words: P2P network,Social norms,Boycott,Free-riding,Incentive mechanism