To study the influence of the thermal characteristics of the motorized spindle of ball bearings on its performance,the heat source calculation and the thermal characteristic simulation of the bearing were performed.The heating consumption of the bearing was analyzed by the local heat calculation method.It is found that the influence of the bearing speed on thermal consumption is greater than that of axial load,and the ball’s spin is the main form of the ball bearing heating.Based on the calculation results of heat source,the steadystate and transientstate analysis were performed respectively by ANSYS under a certain speed with no load.The result shows that the highest temperature appears in the iron core of the motor rotor.The thermalstructure coupling analysis was carried out by loading the steadystate thermal analysis results to the finite element model.The results show that the maximum axial displacement appears at the front of the spindle,and the maximum axial stress appears on the contact point between the ball and the outer ring of the front bearing.An experiment of temperature rise measurement was performed by a no load spindle,the measuring results verified the accuracy of the simulation results.