The existing integrated methods are mainly aimed at the layer of database system. In view of the shortage of those methods, the integration method in the application layer was focused on. According to a new perspective of access control for the database application system, the access control layer was separated from the application layer. A new method called as “fusion” access control was put forward. Based on the method, a simplified integration method of heterogeneous database application system was proposed. An example was shown about how to apply the simplified integration method to achieve the integration of heterogeneous database application system, and the advantages of the new method were verified by a comparison analysis.