Abstract: Due to the differences in the material properties of ceramic bearings and steel pedestals, the non-uniform variations appear in the outer ring fit clearance and bearing internal contact state, which exacerbates the vibration and instability of the CMSS (ceramic motorized spindles system). Therefore, a five-degree-freedom outer ring clearance fit model is established, and the dynamic variations of the internal clearance are considered in the bearing quasi-static model, finally the dynamics model of the CMSS is established. The nonlinear factors caused by raceway-ball contact and outer ring- pedestal contact is considered in this model, and the nonlinear variations caused by thermal deformation and interference fit on outer ring fit clearance and internal clearance of bearing are discussed in detail. The effects of rotation speed, outer ring fit clearance and internal clearance on vibration characteristics and stability of CMSS are analyzed. The results indicate that thermal deformation increases the nonlinear excitation of the spindle system. The increase of outer ring fit clearance will increase the external excitation of the spindle system but will not make the system enter chaotic motion, while the influence of internal clearance on the motion state of the spindle system is more obvious, and the increase of external clearance will shorten the range of internal clearance in periodic motion