Abstract: In order to reduce the temperature control risk for the test pieces in the vacuum environment, the temperature control of the pieces in the thermal vacuum test system is studied in this paper, and the principle of the cascade PID temperature control strategy is analyzed. By the multi-partition and the parameter self-tuning based on the cascade PID control algorithm, a method is proposed for controlling the temperature of the test pieces suitable for a system with a large time lag. The validation test results show that with the proposed temperature control method applied to a power amplifier of a satellite in the thermal vacuum test, a high accuracy of ±0.5 ℃ and a small overshoot of only 0.7 ℃ can be achieved, and the temperature rising and cooling rate is greater than 1.5 ℃/mm.