In this study we do for the thing to develop automatic geometry design program of a mechanical element that we have used in CAD/CAM system. The program, which produces automatically three-dimensional surface and a solid model that have been used in CAD/CAM system, widely create automated two and three-dimensional model to by inputting several necessaries for a design, fur the design element. It is emphasized if you are just a beginner having only basic knowledge of the mechanical engineering, you might be able to design easily a three-dimensional model. The software to be used to develop automatic geometry design program is visualLISP to be a developer program of AutoCAD.