The technique of muhi-agent has been largely used in the development of large-scale and distributed management systems. Trust between agents in multi-agent cooperation can severely affect the efficiency of multiagent system （MAS）. Most trust models presented are based on the Internet peer-to-peer environment. They do not fit for the environment of MAS. Considering the trust characteristics in MAS, this paper gives a novel agent trust model in MAS which is based on credit and relationship web of agent. Theoretical analysis and simulations show： this model can improve the agglomeration of the agent relationship web, and can improve the efficiency of the selecting of cooperative agent; furthermore, compared with the current global model, in agent successful cooperation ratio in the environment which needs agents repeatedly cooperating with each other, in controlling the agent malicious recommendation, the agent cooperative cheating, and in the partiality for the new agent when an agent selects its cooperative partner, this model is more compete. It has both theoretical and practical value on the copartner＇s selection in supply chain management system and e-commerce system