Abstract: On the basis of sustaining the satellite function in a good condition, when the satellite volume, size and mass keeps decreasing, a large amount of heat will be transferred from its inner space, and the conventional thermal control technology cannot satisfy the controlling needs. To keep the stability of load temperature within permissible range, new reasonable thermal control methods are needed. Based on the model of Nano-satellite's temperature system, by combining the on-line self-tuning of PI parameter controller with spacecraft thermal control technology, a new intelligent control system was established to realize the radiator adjustment. Simulation results indicate that the fuzzy self-tuning PI controller can obtain quick response, good adaptability and robustness, and eliminate the steady-state error as well. The new controller is superior to the fuzzy controller and traditional PI controller in that the former works with higher dynamic and static performance.