In an open distributed environment, traditional centralized trust mechanism for e-commerce becomes difficult to adapt to it. The existing P2P trust models are propitious to this environment, but they can not directly be used in e-commerce as taking no consideration for characteristics of e-commerce. This paper combines P2P trust model and e-transaction characteristics, presents a new P2P-based trust model for e-commerce. By computing interactive experiences, recommendations of other peers, risk factors and the transaction context, the model evaluates every peer's globe trustworthiness in order to guide transaction participants. Results of Simulation experiments show that, compared with some current trust models, the new model is effective against malicious behavior.