Abstract: In the process, the paper proposes a kind of local credibility model to calculate the credibility of P2P networks.According to the network transactions between nodes, calculation system of time and space overhead, based on the principle of minimum cost system from the network node selecting numbers of local center node, to replace the traditional centralized model of the single center, complete system the credibility of node calculation, and this prevents the traditional central model center node calculation long time consuming.Experiments show that the method can reduce the credibility of the calculation, time-consuming, and improve the calculation of real-time, timely and effectively protect the network security.