Abstract: Solving geometric constraint system is the central issue of parametric design. The strategy with a parametric design capability based on the combination of declarative and constructive constraints is described in this paper. The closed loop of constraints of constructive sequence is solved by changing the redundant constraints to shape degree of freedom, and the clipping and reducing operations are used to decompose under and fully constrained system. And it has been implemented in a CAD system of MDS 4.0.