Abstract: On the basis of the studies of the current packing methods, this paper presents a constraint based algorithm for packing problems. Using the degrees of freedom analysis borrowed from techniques originally devoloped for the analysis and synthesis of mechanical devices, the algorithm solves packing problems alternately in two levels:higher level and lower level. A packing order is planned in higher level and the numerical positioning is performed exactly in lower level.The algorithm is a better method for packing problems because of several remarkable features in generality and expandibility.