There are a lot of security issues in cloud computing service environments such as virtualization, distributed big data processing, serviceability, traffic-handling, application security, access control, authentication, cryptography and etc. Especially, data access using various resources needs authentication and access control model for integrated management and control in cloud computing environments. In this paper, the authors propose Onto-ACM (Ontology Based Access Control Model) for dynamic access control. Onto-ACM is a semantic analysis model for permitted limit of service provider and user. This proposed model is the intelligent context-aware access model for applying the proactive security level of resources access using context information ontology modeling and reasoning engine.