Abstract: Bearing-rotor system is a key part of rotating machinery. Among them, full ceramic ball bearing has some excellent characteristics that bearings of other materials do not have, which is irreplaceable in some fields. In this paper, the dynamic model of unbalanced rotor considering the fit between full ceramic ball bearing and steel pedestal is established. This model fully considers unbalanced mass of rotor and the difference of deformation between full ceramic ball bearing and steel pedestal due to different materials under the influence of heat. The influence of the clearance between full ceramic ball bearing and steel pedestal on dynamic characteristics of unbalanced rotor is analyzed. The simulation analysis of the model is carried out, and the response laws under different speeds, unbalanced masses and clearances are obtained and the results are verified through an experiment. The research results have certain guiding significance for the understanding of vibration characteristics and fault diagnosis of ceramic bearing-rotor system.