Abstract: A virtual prototype model has been established by 3D modeling software Pro/E．On condition that the column and the beam as key parts are set to flexible，a rigid-flexible virtual prototype model has been established by the finite element software ANSYS．The paper discusses the flexible effect of the key parts on stability of the machine tool．Improvement of the key part structure can effectively improve the dynamic characteristics of CNC machine tools．The result shows that the dynamic characteristics of the machine tools can be more accurately reflected by simulation analysis based on the rigid-flexible coupling model．The overall dynamics performance of the machine tools can be predicted and evaluated comprehensively in the environment without physical prototype．This work has offered a feasible approach to establishment and research of the rigid-flexible virtual prototype．