Abstract: A Dtree decomposition algorithm was presented to solve the wellconstrained and underconstrained geometric constraint problems. Firstly， as a preliminary work， a broader range handling strategy was proposed which could unify the special constraints with the ordinary constraints. A transformation strategy was used which could transform the underconstrained geometric constraint problem into wellconstrained geometric constraint problem. Secondly， according to properties of the degree of nodes in the geometric constraint graph， the Dtree decomposition algorithm was proposed， which had a lower computational complexity and the same solution domain compared with the classical algorithm. Finally， according to the regularity of the Dtree decomposition algorithm’s results， a export strategy to numerical constraint solver’s solving sequence was presented. The solving sequence exported by Dtree decomposition algorithm could improve the solving efficiency of geometric constraint solving’s numerical solution.

Key words: geometric constraint solving, the graph approach, special constraints, decomposition analysis, solving sequence