On the basis of the existing satellite active thermal control strategy, in order to reduce the power of the thermal control subsystem and reduce the energy burden of the whole satellite, this paper proposes an autonomous suppression method for spacecraft thermal control power, which takes the total thermal control power as the control target, coordinates the working state of the electric heater, and compresses the electric heating power in the process of autonomous thermal control. The on-orbit test verifies that the thermal control power in the process of autonomous control is reduced by 24.8% and the duration of peak power by 62% on the basis of meeting the thermal control requirements, and the temperature fluctuation is well suppressed, the optimization effect is remarkable. The suppression method has been applied on many satellites and achieved the expected results, which can provide a reference for the autonomous and intelligent design of spacecraft in the future.