Cerium　tungsten　electrode　was　heated　in　the　analysis　chamber　of　X-ray　photoelectron　spectroscopy　(XPS)　system　at　different　temperatures.　The　evolution　of　the　valence　state　of　the　main　elements　on　the　surface　of　the　cerium　tungsten　electrode　material　was　monitored　by　in　suit　XPS.　It　was　found　that　the　cerium　on　the　surface　of　the　sample　in　the　initial　state　was　mainly　in　the　form　of　Ce4+　and　Ce3+.　During　the　heating　process,　Ce　3d　core　energy　level　spectrum　changed.　With　the　temperature　rised,　the　content　of　Ce4+　in　the　samples　decreased　gradually.　It　can　be　seen　that　a　part　of　Ce4+　is　converted　to　Ce3+　during　the　heating　process　of　the　cerium　tungsten　electrode　material.　That　means　cerium　in　the　cerium　tungsten　electrode　material　has　a　tendency　to　be　restored,　this　will　promote　the　electron　emission　and　enhance　the　performance　of　the　electrode　material.