The influence to CNC machining center caused by natural frequency is often been considered at the beginning of the design,but due to the inevitable errors in manufacturing process,it is indispensable to carry out the dynamic characteristics analysis for the using CNC machining center and obtain its modal for the optimization of machining center. The ANSYS finite element modal analysis, the hammering method of experimental modal analysis and waterfall diagram analysis of the vibration signal in the process of speed up for KVC800 vertical machining center were carried out. Through comparison and verification,it was found that the machining center had the lower modal in its working frequency. The dynamic cutting test verified that the low order modes made the accuracy of workpiece lower. It provides a reliable basis for optimizing operation of machining center.