Abstract: In ubiquitous computing environment user move frequently and access resources anytime and anywhere. Ubiquity and invisibility are the distinct characteristics of ubiquitous computing. Numerous entities are always unknown to local system. The security service should consider the factor of time, location and trust to enhance the security of interaction between each other. The exiting access control consider just one dimension, temporal, spatial or trust. In this study, we propose a new access control model supporting these three dimensions simultaneously. The proposed access control model can effectively support various ubiquitous computing environments.