Mechanical stiffness reflects the ability to resist deformation of the mechanical structure. In the low speed or overloading,the system stiffness deficiency can cause creep phenomenon of machine tool, thereby the positioning precision, dynamic stability and response speed of the machine tool are reduced. Simulink simulation analysis was used to analyze the influences of torsional stiffness and axial stiffness of mechanical transmission mechanism on the movement stability of feed system. The simulation results show that the effect of the axial mechanical stiffness on the stability of the feed system is much greater than that of the torsional stiffness.So the way that through increasing axial stiffness to control movement unstability caused by insufficient stiffness should be paid more attention.