The shape design of products is the primary activity of design process. The research on qualitative & imprecise solid modeling for computer-aided conceptual shape design is presented in this paper. At first, the requirements of shape representation for computer-aided conceptual shape design are emphatically discussed. Secondly, in the situation where the product information is deficient, the ideas of qualitative and imprecise solid modeling are presented to deal with qualitative and imprecise information in the phase of conceptual shape design. The aims are mainly to explore the representation and manipulation of product shapes, and to benefit designers to design shapes in the phase of conceptual design. Finally, a prototype system CACSD is briefly introduced to implement the relevant ideas.