Using Pro/Toolkit and parametric design technology to develop a software applied in Pro/Engineer which is attended to design cam. There are some inefficient aspects in cam design, such as a lot of work should be needed in process of getting the cam profile. It's hard to draw the cam profile without equation. Different kind of cam needs several kinds of methods to build. This paper introduces parametric technology and method of combination of Pro/Toolkit and VC++, which develops a software used in Pro/Engineer. This software can be applied in cam design. This paper briefly introduces the function database of Pro/Toolkit which interfaces with Pro/Engineer. Using Pro/Toolkit deeply studying the setting, process, method and corresponding tools in the further development of Pro/Engineer. This paper particularly studies user interface technique, feature build technique and parametric design technique. It carries out further development of standard part library, analyzes the successful theory and the key method of every technique and builds particular developing process. Using the technology of Pro/Toolkit, we edit the menu, create and activate them in application to realize the simple user interface, but it is difficult to create resource files when we need complicate dialogs with graphics to get parameters information. After solving the problem of Pro/Toolkit communicating with Visual C++ and the problem of MFC (Microsoft Foundation Class), communicating with database, we can easily create any type dialogs we want. The software adopts means combined with face to object technique and face to process technique, and it achieves the development of cam parametric design with the using of Dynamic Link Library(DLL). The software can be separated into several module, including user interface, cam classify, calculating and drawing cam contour cam solid build. This paper can supply a plug-in software of Pro/Engineer used to design cam.