Abstract: The change of design procedure caused by Concurrent Engineering is a big challenge for existing mechanical CAD system. In order to enable existing CAD system to support Concurrent Engineering, this paper present an assembly based modeling method to manage the parameters and geometry models in concurrent design environment. Firstly, a data model, which can describe the assembly relations, parameter relations and hierarchical structure among parts/components of mechanical product, is proposed. Then the function and the working procedure of this system is illustrated using an example.