In　this　paper,　commercial　Ce-W　cathode　was　selected　as　research　object.　The　cathode　working　environment　was　simulated　by　heating　in　an　ultra-high　vacuum　(UHV)　chamber.　Scanning　electron　microscopy　(SEM),　Nano-scanning　Auger　electron　spectroscopy　(AES)　and　X-ray　photoelectron　spectroscopy　(XPS)　were　used　to　study　the　surface　morphology　and　chemical　states　from　900　degrees　C　to　1200　degrees　C.　The　results　showed　that　W6+　disappeared　and　the　surface　of　the　cathode　was　composed　entirely　of　W-0　in　heating　process.　The　content　of　Ce4+　gradually　decreased　by　heating　and　cerium　oxide　had　a　tendency　to　reduce.　The　adsorbed　oxygen　disappeared　and　the　lattice　oxygen　was　present　in　CeO2　and　Ce2O3.　Moreover,　when　raising　heating　temperature,　the　rare　earth　oxide　diffused　from　the　aggregation　areas　to　the　tungsten　matrix　surface　to　form　an　active　layer.　The　surface　cerium　oxide　was　highest　at　1100　degrees　C.　Then　the　thickness　of　active　layer　was　about　6　nm.　At　1200　degrees　C,　the　evaporation　rate　of　cerium　oxide　on　the　surface　was　greater　than　the　rate　of　migration　from　the　body　to　the　surface.　And　the　loss　of　the　surface　active　layer　was　severe　at　1200　degrees　C.