To determine the heat insulation performance of the thermal protection materials cladding the gas cylinders， a thermal vacuum test is implemented on two species thermal protection sets， with a radiant heat source simulated by a quartz lamp heater， and the atmospheric environment simulated by a vacuum tank. Results indicate that two species thermal protection schemes are both satisfied within the upper limit of the temperature， and the heat insulation property of the combination thermal protection structure “flexible insulation+ middling temperature MLI ” has better insulation performance. The indeterminacy of the thermal analysis method is evaluated by comparison with the result of the thermal test. The test data may server as a reference for future thermal protection design of spacecrafts.