With the development of mobile computing, a more intelligent location aware access control approach which can not only protect the privacy of location information but also reduce the frequency of access control decision is needed. This paper brought semantic access control approach into the Location Aware Access Control (LAAC). First, we used semantic area to substitute physical location for the authorization decision, reducing the frequency of authorization decisions. The exact physical location of the subject would not be exposed. Secondly, for the different representation of semantic area of different security domains, we used ontology cluster to represent semantic spatial information. We established security domain ontology (SDO) and bridge ontology (BO) between the security domains. And then we used such ontology cluster as knowledge base and added annotation to the physical areas of XACML language. Finally, the model and framework of location aware semantics based access control for mobile computing is proposed. The proposed location aware semantic access control(LASAC) approach provides a better solution for location aware access control in mobile network environment.