Abstract: The thermal conductivities of a low-density mullite were tested by guarded hot plate method at temperature of 150-500℃. The influence of test parameters such as testing temperature, pressure, specimen thickness and temperature difference on the test results were analyzed. On this basis, three groups of calculation models of thermal conductivity of the low-density mullite were obtained. According to the actual test results, these three groups of calculation models were verified respectively. The results show that the thermal conductivity of the low-density mullite specimen increased with the increase of test temperature. The relative deviations of temperature-pressure and temperature-temperature difference calculation models were less than 5% in the selected temperature range, and the relative deviation of temperature-thickness calculation model was less than 10% in the selected temperature range.