The basic way and method to apply the equipments CAD data to a geometry description system (GDS) are presented, and its interface to GDS is set up. The basic function, flow and implementation technique of the interface are analyzed. Special computer software is programmed, and an application example is given also. The research results indicate that this interface can assist to derive desired data from the CAD data, and provide powerful technical support for the development of a practical data transferring interface.