The high temperature properties and corresponding microstructure of high temperature Mo alloys (Mo La alloy) and TZM Mo alloy were studied at 1000 – 1800 degrees. The results show that under the condition of less than 1400 degrees, Mo La alloy has high strength and plasticity of the comprehensive performance, when the temperature is greater than or equal to 1400 degrees, the tensile strength of La Mo alloy decreased obviously, and the plasticity of La Mo alloy also decreased significantly. However, with the increase of test temperature, the tensile strength of TZM alloy decreases, but the ductility of TZM Mo alloy increases, which is opposite to that of La Mo alloy. At the same time, TZM alloy has obvious advantages over Mo alloy at the same temperature, whether it is strength or plasticity. The microstructure observation shows that two kinds of molybdenum alloys begin recrystallization at 1100 degrees and continue to 1550 degrees centigrade, and their recrystallized grains all appear elongated structure, which is obviously different from the equiaxed grains of pure molybdenum recrystallization.