As the networks connect the world, enterprises tend to move manufacturing activities into virtual spaces. Since different applications use different data terminology, it becomes a problem to interoperate, interchange, and manage electronic data among different systems. According to RTI, approximately one billion dollar has been being spent yearly for product data exchange and interoperability. As commercial CAD systems have brought in the concept of design feature for the sake of interoperability, terminologies of design feature need to be harmonized. In order to define design feature terminology for integration, knowledge about feature definitions of different CAD systems should be considered. STEP (Standard for the Exchange of Product model data) have attempted to solve this problem, but it defines only syntactic data representation so that semantic data integration is unattainable. In this thesis, we utilize the ontology concept to build a data model of design features which can be a semantic standard of feature definitions of CAD systems. Using the feature ontology, we implement an integrated database and a simple system which searches and edits design features in a semantic way. This thesis proposes a methodology for integrating modeling features of CAD systems.