Abstract: In order to correctly describe the characteristic information of parts in the system of intelligent computer aided process planning (CAPP), the authors present a method to build model for gyratory parts by means of character modeling technique. In this method, modeling element is not the commonly used geometric element such as point, line, surface, but the characteristic one through which the geometric and characteristic informations can be transferred into the system, so that the description of such shape characteristic element as size, tolerance, surface roughness of gyratory parts is completed.