Abstract: P2P system lacks effective mechanism in terms of peers because of its open nature and user anonymity，so its peer trust cannot be evaluated efficiently，and then reliability of the system will be influenced by the possible cheating peers.Aiming at the security problems，a network trust model based on subjective logic theory（created by JΦsang） can be a better solution.The model is to confirm appropriate value of trust degree and the trustiness proportion among the uncertainty by calculating its weighed average and variance.What’s more，risk mechanism is introduced on the basis of the trust model.With the help of all the processes，the trust model can prevent from collaborative cheating and imputation to some degree.According to the simulation analysis，it turns out to be that the trust model is effective to solve the security risk existing in P2P network.

Key words: subjective logic, weighted average, reputation, risk

摘要： 由于P2P系统的开放性、匿名性等特征，使得P2P系统对节点实体缺乏有效的管理机制，节点间的信任度无法进行有效的评定，就有可能存在欺诈节点，影响系统的可靠性，针对以上问题，在JΦsang主观逻辑理论的基础上，建立了一种基于主观逻辑理论的网络信任模型，该模型通过加权平均和方差来确定信任程度的取值方式，以及不确定度的可靠成分的确定，并在信任模型的基础上添加了风险机制，可以在一定程度上防止协同作弊和诋毁的安全隐患。通过仿真分析表明，这种信任模型能很好地解决P2P网络中存在的安全隐患。

关键词: 主观逻辑, 加权平均, 声誉, 风险