Abstract: This paper summarises the difficulties met in representating the mechanical product feature information by single CSG model or B-ReP model. According to the special requirements of integrated CAD/CAM systems, an method of feature information representation is proposed based on the CSG + B-ReP data structure. The main characteristics of the method are that face is used as an unit for the feature definition; and making use of the coordinative relationship of CSG aad Rep in the FSMTS (Feature Solid Modelling Tool System), product information table (PIT), CSG, and B-ReP are linked up to form an adjacency list. As the result, the parametric product model can be set up by the CSG description; the geometry can be defined, and the feature information can be added interactively throngh the B-ReP model.