Abstract: The chemical reaction of La₂0₃ and Mo₂C in La₂0₃-Mo cathode materials have been studied by thermal analysis, X-ray diffraction and scanning electron microscope. The experimental results show that La₂0₃ and Mo₂C can have a chemical reaction at high temperature to produce metallic lanthanum and molybdenum. The reactants in different existing state react in different temperature. The reaction temperture(l 203 K) between powdered La₂0₃ and Mo₂C is lower than that in La₂0₃-Mo cathodematerials (1 503 K). It is proved for the first time that the reacted metallic lanthanum appears at the surface of this kind of material at high temperature.