Abstract: Due to its compact structure, the motorized spindle cannot transmit the heat generated internally to the external environment in a timely manner, resulting in thermal errors in the machine tool. The heat generation inside the motorized spindle is calculated by using the thermodynamic knowledge, and the boundary conditions for heat exchange between the motorized spindle and the external environment are determined. The steady state thermal and thermal structural indirect coupling of the motorized spindle are analyzed in Ansys. The results show that the highest temperature inside the motorized spindle is located at the contact between the rotor center and the shaft core, reaching 62.395 ℃. The maximum axial displacement of the motorized spindle is 37.91 μm, located at the tail end. Therefore, while strengthening the heat dissipation of the motorized spindle core, it is necessary to compensate for thermal errors to ensure the machining accuracy.