In the light of the problem that the current trust model is mostly role-based trust model, yet this trust model doesn’t take attribute and cross-tenant access into account, which is not suitable to the dynamic multi-tenant cloud environment. In this paper, we propose a trust model based on role and attributes, including subject attributes, resource attributes and environment attributes; and this model includes single-tenant and multi-tenant trust sub-models. Analysis shows that the proposed trust model can resolve the problem that when attributes fulfill the requirements but the users’ or roles’ credibility is low. User Role Assignment and Role Permission Assignment will reduce the security of tenant’s data and trust problem between tenants when the users access tenants. So it can be applied to access control in multi-tenant cloud environment.