本文提出了一种计算机表达的机械零件模型。它把描述零件的信息分为三个层次：零件的总体描述层、零件的语义层和零件的几何层。在零件的形状建模中，语义层中的形状元素、几何居中的信息及它们之间的联系同时建立。制造活动所需的零件信息通过语义层提供。 This paper presents a mechanical representation of computer parts model. It divides the information describing the parts into three levels: the general description layer of the part, the semantic layer of the part and the geometric layer of the part. In part shape modeling, the shape elements in the semantic layer, the geometry centered information, and the relationships between them are also established. Part information needed to create an activity is provided through the semantic layer.