Abstract: Satellite-borne microwave module is the most important,most complicated and costly sub-system,which determines the performance of satellite-borne radar system.The characteristic and importance of the thermal design of satellite-borne microwave module are introduced in this paper.After studying two kinds of heat exchange,thermal contact transfer and thermal radiantion transfer,the corresponding methods of structural design to improve heat emission efficiency of the module are suggested.At last,this paper also introduces the thermal vacuum test.Its characteristics,the importance and the main test steps are discussed.Thermal vacuum test provides an important reference for the thermal design of satellite-borne microwave module and for the optimal design of aerospace products.