Abstract: A mechanism for supporting the top-down design of products modeling is developed．The representation of product function and the object-oriented product modeling are realized by the black-box multi-tree model and the design variable constraint network（ VCN） ．The algorithm of classification-step-decomposition is applied to solve the VCN．In the integrated design environment，the 3D layout and the relational model for product design are created dynamically in the process of designing typical parts．