Based on boring and milling machining center spindle, under the conditions of the environment temperature and convection heat transfer coefficient of boundary, heat transfer law of the motorized spindle under the action of heat load was analyzed. The distribution rule of the spindle in three-dimensional steady-state temperature field was gotten. Based on the coupling theory of thermal structure, the change laws of stress and strain of the spindle were studied. It provides a theoretical basis for high-speed motorized spindle structure design and optimization.