the parts library system of three dimensional parametric design of planetary gear base on CS structure which use SoildWorks as the CAD development platform, which establish the base parts library, can automatically generate the required size specifications of the parts. The parts library adopts template file as the driving source, openness of strong, fast to run, convenient for management and maintenance, is a kind of ideal driven approach so far, this method is also suitable for a parametric function and the development interface of the CAD system, such as Pro/E, UG, etc.