The control moment gyroscope(CMG) is a critical actuator in spacecraft attitude control systems. In the vacuum of space, heat generated by the CMG is primarily dissipated through thermal conduction and radiation, resulting in substantial temperature rises that may compromise system stability and reliability. Consequently, analyzing the CMG’s temperature field and maintaining its operating temperature within acceptable limits is essential. This study focuses on a 70 Nms single-frame CMG, for which a thermal simulation model is developed to investigate temperature distribution and assess the effects of rotational speed, applied torque, and bearing preload on thermal behavior. The model, validated against experimental data, achieves an average temperature prediction accuracy of 93.87%. Results reveal that temperature at various measurement points is highly sensitive to changes in rotational speed. The lower end of the rotor shaft exhibits a pronounced responsiveness to torque, while both ends of the rotor shaft are significantly influenced by bearing preload. The maximum observed temperature increase is 5.2 ℃ at the lower end of the rotor shaft, whereas the frame experiences the smallest increase at 1.72 ℃. The presented temperature field modeling approach offers valuable insights for optimizing the design of control moment gyroscopes and facilitating operational diagnostics of spacecraft systems.