Abstract: It is necessary to explore the interference fit amount under the influence of rotational speed and the temperature rise and the rules of change of dynamic characteristics of spindle system. Considering the inner ring centrifugal expansion aroused by the speed and the thermal displacement caused by temperature rise,an interference fit model of bearing was established in this paper. Then the interference fit model was coupled into Harries bearing dynamic model,the bearing dynamic model was established with consideration of the interference fit,and based on the Timoshenko theory,a finite element model of machine tool spindle system was established. Conferred on the self-built spindle system in laboratory,the effect of interference fit impact on the dynamic characteristics of spindle was analyzed. The results show that the bearing inner and outer ring initial interference amount increases,and the original contact angle linear decreases; the initial interference fit amount under the influence factors of temperature and centrifugal force increases; the initial interference quantity and inner ring centrifugal expansion and thermal expansion leads to the bearing stiffness increase,and the increase of bearing stiffness leads to the increase of natural frequency of spindle system,and compared with the first and second order natural frequency,the degree of three and four order natural frequency affected by the factors is larger.