Abstract: In order to meet the requirement of the passive intermodulation(PIM) testing in a space environmental simulation chamber and to study the impact of the temperature changes on the performance of the spacecraft system-level PIM, a low-PIM absorbing environment has to be established in the chamber. The method adopted in this paper is to install a low PIM wave absorbing device in the chamber, so that the passive devices under the test is completely covered by it, and then the testing is completed by simulating the temperature strain process. The design philosophy and the atmospheric thermal cycling test process of the low-PIM absorber with a PIM index less than -150dBm are described. The testing results are analyzed, and the PIM performance of the absorber is shown to be able to meet the test requirements.