Abstract: Because the different CAD systems use different concepts, attributes and relations to store data model, it is difficult to implement semantic interoperability among heterogeneous CAD systems. In this study, the Feature Command Ontology Model (FCOM) which is established, includes a number of Neutral Semantic Feature Commands (NSFCs) corresponding to the basic modeling operations of CAD systems. The FCOM which has explicit ontological semantics, provides the uniform representation of heterogeneous information and helps to shield the heterogeneity of data sources. Meanwhile, it is capable of dealing with modification and deletion operations besides common creation operations. Based on the FCOM, a synchronized collaborative design platform upon heterogeneous CAD systems is built; the real-time data exchange among heterogeneous CAD systems is achieved in a semantic way.