The heat source distribution of engine in altitude simulated test is relatively similar to real flight case compared to the normal pressure test case. In this article， the correctness of high temperature heat shield design is validated through altitude simulated test. The heat transfer model is modified by considering the gas conduction and contact conduction between each layer in high temperature heat shield. This thermal model has a relative high precision to the data getting from the altitude simulated test. Thermal model of the main engine and high temperature heat shield in altitude simulated test is made. Then， it is modified by considering the infrared radiation and the heat conduction with the gas in vacuum chamber.