The authors review current research situation of engineering CAD, including engineering con-straints and geometry constraints, and analyze the denotation and characteristics of engineering design. Somerules and peculiarities of constraints in engineering design are analyzed. Engineering constraints representationmodel named as “Multilateral Elements Constraints Graph”, and the method based on the model constructs theone-way dependence relations between constraints variable are analyzed. In this way, some problems of constraints consistency and search space are solved well.To bridge the gap between the constraints solver and special engineering domain,an improving algorithm based on priority list is developed.Many heuristic rules and engineering experiences could be added to the list for the efficiency.These algorithms have been used in the CAD system of plant steed structure design.