Abstract: Taking AutoCAD for windows as the supporting software, using ADS in Windows asr system developing means, and employing the manner of modularization and gradual enlargement as well as OOP method, we have leveloped a three-dimensional parametric CAD system (WFCAD) of welding fixtures. The WFCAD system can complete the weld workpiece's information processing, fixture size computing three dimensional model drafting, three-dimensional dynamic simulation, and making the assembly and parts drawing from three-dimensional model drafting. The WFCAD system has good extending property, opening property and a good man-machine interface. The handsome and compact standard Windows man-machine interface is used in WFCAD system.