Nowadays, e-commerce is becoming more and more popular for trade in the real world and facing a fundamental and challenging research topic due to peer anonymity, peer independence, high dynamic and stochastic of peer behaviors, and the absence of an effective security control mechanism. Mutual trust, which enables transacting peers to overcome the uncertainty and risk inherent in the environment, plays a important role in making the prediction of whether one transaction is safe or not. In this paper, We propose a uncertainty trust model to evaluate trust which can reduce the risk of malicious behaviors. Our approach combines uncertainty and time factors into the trust model in a practical way.