P2P(peer-to-peer) networks have dynamics, anonymity, scalability and other features. Because P2P applications are a dispersed, decentralized, uncontrolled spontaneous behavior, and has anonymous release characteristics, how to control the information content of security has become a problem. In the P2P network environment, the behavioral characteristics of the node analysis method were introduced on the basis of multiple digital signatures based on PKI, and assorted the behavior of the nodes into different grades. According to different levels, it gave a different coefficient of the ratio points, made a more reasonable value of the node’s credibility, and better avoided the nodes with high reputation values to get malicious attacks. It improved system security and reliability on the whole.