The thermal and mechanical characteristics of motorized spindle interact with each other,using shaft core cooling can reduce the temperature rise of motorized spindle,but also affect its mechanical characteristics.The thermal characteristics,static stiffness and dynamic response of 150SD motorized spindle with core cooling structure were tested.The effects of shafe core cooling on the thermal-mechanical characteristics of motorized spindle were studied.The results show that through shaft core cooling,the thermal balance time and axial thermal deformation of the motorized spindle system are reduced,but the static stiffness and the first and second order natural frequencies of the system are reduced at different rotating speeds.It is necessary to carry out comprehensive optimization design from the aspects of overhanging amount,span and geometric size in the design stage to improve its mechanical characteristics.