Abstract: This paper aims to solve the problem of abnormal rotation error that occurred in a domestic brand motorized spindle. The abnormal rotation error of the motorized spindle is caused by the gas seal failing to play a good sealing effect, which causes the front bearing and disc spring polluted by grinding oil, thus resulting in the failure of the front bearing, the worn of the spindle shaft and the decay of broaching force. By improving gas seal pressure, the material of the spindle shaft, and the structure of the broach, the service life of a motoried spindle is increased by more than 100%.