The high-speed electric spindle is the key part of the machining center which performing high speed precision machining. In order to ensure the electric spindle running under the smooth and steady state, it is necessary to prevent and discover the abnormities during the running process of the electric spindle by the experimental test and analysis. In this paper, the vibration order analysis method combined with the experimental modal test is utilized to measure and diagnose the abnormities of a high speed electric spindle.

By the experimental modal testing to the main structure of the high-speed horizontal machining center，the modal parameters such as the natural frequency, damping ratio, stiffness and mode shapes are obtained. By analyzing the vibration characteristics, the critical components of the machining center is at the spindle front bearing part and the vertical column on which the screw driving spindle box to move in vertical direction is mounted are determined, and provide an important basis of optimizing the structure for the machining center. And the amplitude-frequency characteristic curves of the critical components evaluate the dynamic stiffness as the key indicators to provide reliable data for improving processing accuracy and cutting ability of machining center.