In this paper, we propose a new dynamic resource allocation scheme - Access Control-based Resource Allocation (ACRA) for cloud users in order to address some deficiencies of the current resources allocation mechanisms in some free cloud computing environment. The proposed scheme comprehensively analyses behavior characteristics of cloud users and evaluates user behavior trust using fuzzy analytic hierarchy process (FAHP), and then dynamically adjusts the resources permission of cloud users according to their behavior trust values, thus effectively controlling user resource utilization. Experimental results show that the ACRA scheme can provide basis for allocating resources dynamically and reasonably to cloud users with different behaviors and improve resource utilization in cloud computing systems.