Abstract: In the thermal vacuum test for spacecraft subassembly, when two specimens are tested in a same space environment simulator, the mutual temperature influence between them due to the difference of their thermophysical property and test requirements should be avoided. An effective method to reduce this influence is to separate them by using a cold plate, which requires that its temperature must be consistent with the heat sink of the space environment simulator in the test. In this paper, a new type of cold plate is designed, based on the finite element analysis of the finned pipe, which can reduce the influence to the smallest degree. The test results indicate that this type of clapboard can be adapted to various cases in the thermal vacuum test.