Abstract: Rotation accuracy is one of the basic indicators to measure the performance of machine tool spindles. As the supporting component of the spindle system, the dynamic characteristics of the bearing are closely related to the rotational accuracy of the spindle. During the operation of the spindle, the internal clearance of the bearing increases with the increasing wear of the spindle bearing. Based on the dynamic model of spindle, the effect of bearing clearance on spindle rotational accuracy is studied in this paper. Based on Gupta bearing dynamics modeling method, a radial clearance model inside angular contact bearing was established, which was introduced into the spindle bearing-rotor dynamics model. The influence mechanism of radial clearance inside bearing on spindle rotational accuracy was studied theoretically and simulatively.The results show that the rotational error of the spindle increases as the radial clearance inside the bearing increases.