Abstract: Space large rotating payloads, being complex in structure and constantly rotating, are a challenge to the test validation of their thermal characteristics. A case study of the thermal balance test method of the microwave scatterometer in Haiyang-2 satellite is presented. A direct validation method is used in the engineering model phases, which Call used to forecast the in-orbit temperature directly from the ground test result. Meanwhile, all indirect validation method is used in the flight-model phases, which may used to predict the in-orbit temperature through the thermal analytical model. A comparison between the thermal test results, the thermal analytical results and the flight results shows the correctness and the effectiveness of the thermal balance test.