The article first analyzes the characteristics of the control objects in thermal vacuum tests, points out the main problems and difficulties existence in the temperature control currently. Fuzzy PID controller is designed according to these characteristics. In order to verify this control method, three times of thermal vacuum tests are carried out. Results show that this FUZZY PID control method has a small amount of overshoot, super adaptability without manual operation in the test. It provides a better solution to the problem in current control system short of intelligence and having a large quantity of overshoot, which greatly reduces the job intensity of test personnel on duty.