Abstract: With the rapid development of P2P network in recent years,there are a lot of ‘free-riding’ node problems．A kind of balanced algorithm was proposed to determine whether a node is free-riding or not．This algorithm not only takes the rational behavior of node itself into consideration but even also the characteristics of the physical environment where nodes exist．And it slows down the speed of downloading resources of a node to suppress the free-riding beha-vior．The simulation experiment shows that this algorithm can inhibit the number of free-riding nodes effectively,but also improve the download success rate of the network．It enhances the fairness and stability of network．So finally it achieves the purpose of suppressing the fee-riding.

Key words: P2P network,Free-riding,Effectiveness values,Fairness index