Peer-to-peer network technologies have gained popularity without the need for centralized servers. With the consistent development of the network, the existing techniques about access control could not resolve the security issues in P2P networks perfectly. How to realize the trust mechanism in access control system is an important subject of P2P security research. In this paper, we analyze the lack of trust mechanism in the existing access control models, and present a recommendation trust model based on reputation. We introduce the related concepts in the trust model and explain the mechanism of trust. Then, a protocol of trust query is designed and calculations about trust are given. At last, we validate the availability of the trust model, and applied it in the existing access control model. The combining of trust mechanism and access control technologies makes the P2P networks securer.