Abstract: A self-designed thermal-comparator with automatic-temperature measurement was made on the basis of thermal conduction principle. It could be used in comparison of thermal conductivity (TC) of alloys. The TC coefficients of the novel magnesium-lithium alloys were measured and the results showed the relationship between the thermal conductivity with alloying and heat treated states of alloys. The instrument was the simple in structure,easy to operate and effective in research and exploration of new alloys with unknown thermal properties.