This paper analyzed the dynamic performances of vertical machining center and investigated the problems of dynamiccharacteristics. The modal analysis in both experiment and simulation wascarried out to obtain the modal parameters. The vibrations of the machine spindle were tested to obtain the vibration spectrum under different spindle speeds. It synthesized and compared with the vibration and modal characteristic in order to investigatethe weak parts of the structure. It is concluded that modal characteristic has something to do with the vibration, and there is eccentric between the active rotor and driven rotor. This comprehensive comparison method for dynamic analysis is very effective.