Abstract: 3D geometric constraints solving has important significance for assembly modeling，assembly process planning and concurrent engineering．Freedom analysis can detect the conflict and redundancy among constraints． The numerical method requires good initial value and has problems with stability and robustness．To overcome these shortcomings，we make use of geometric elements on the part such as point，line，plane，cylinder and sphere，so as to solve the geometric constraints by analyzing the spatial relationships of these elements．In such a way，3D geometric constraints are solved more efficiently and stably．