Abstract: In grid environments, trust mechanisms are effective methods which can solve security problems of grid services. The paper studies behavior trust relations among grid services which are organized in the P2P pattern, presents a behavior trust model, and studies the application of D-S evidence theory and improved evidence conflict resolution policies in the behavior trust model. The paper solves trust metric, trust transfer and trust combination in the proposed behavior trust model. Simulations and result analyses show that the model is reasonable, effective and practical.