In mechanical structure design area, many FEM (Finite Element Method) packages are used. But the design using FEM packages depends on an iterative trial and error manner and general CAD systems cannot cope with the change of parameters. This paper presents a methodology for building a designing system of a mechanical structure. This system can generate the drawing for a designed structure automatically. It consists of three steps: generation of a structure by selection of the parameters, stress analysis, and generation of a drawing using CAD system. FEM module and parametric CAD module are developed for this system. Inference engine module generates the parameters with a rule base and a model base, and also evaluates the current structure. The parametric design module generates geometric shapes automatically with given dimension. Parametric design is implemented with the artificial intelligent technique. In older to the demonstrate the effectiveness of the developed system, a frame set of bicycle was designed. The system was implemented on an SUN workstation using C language under OpenWindows environment.