Abstract: To study the performance of heat insulation of the space station with multilayer in ambient environment, based on the 1-D heat transfer model, measurements are made for the heat insulation of a multilayer (MLI) of 15 layers in ambient environment, and the ambient temperature can be adjusted. It is shown that, in the ambient environment, the performance of the heat insulation of the MLI of 15 layers is steady, and is not much affected by the environmental temperature. Within the test error, the equivalent heat transfer coefficient is 0.02 W/(m·K), and the heat resistance is 2.88℃/W, approximately. These results can be applied to analyze the thermal boundary of the space station in ambient pressure heat test, for properly carrying out the heat test in the ambient environment.