Abstract: With the development of the communication satellite technology, the sending and receiving system becomes a common design target for the communication satellite payload, and the passive intermodulation (PIM) becomes particularly prominent. In order to complete the low PIM index test of the satellite transponder system in the thermal vacuum environment, a low PIM heat sink is developed by using the silicon carbide absorbing material. The heat sink not only provides a low-PIM test environment with an indicator of less than 150 dBm, but also enjoys the heat flow simulation function and the microwave power tolerance in the vacuum heat test. The first microwave load wireless PIM test in China is successfully completed with the help of the satellite