Lattice　defects　of　semiconductors　have　a　tremendous　influence　on　the　photo-absorption　and　separation　of　photogenerated　electron-hole　pairs;　thus　the　photocatalytic　performance　of　a　semiconductor　can　be　modulated　by　creation　of　defects　on/in　it.　In　this　work,　WO3-X　photocatalysts　with　oxygen　vacancies　were　prepared　from　highly　crystalline　WO3　by　vacuum　heat　treatment.　The　resulting　WO3-X　samples　with　defects　were　characterized　by　Raman,　XPS,　DRS,　ESR　and　photocatalytic　water　oxidation　experiments.　The　results　revealed　that　the　visible　light　absorption　of　WO3-X　increased　with　increasing　vacuum　heat　treatment　temperature.　The　surface　oxygen　vacancies　of　WO3-X　could　significantly　improve　the　photoelectric　behaviour.　WO3-X　showed　the　maximum　photocurrent　density,　which　is　3　times　higher　than　that　of　the　pristine　WO3,　and　a　much　higher　photocatalytic　activity　than　the　pristine　WO3.　The　surface　oxygen　vacancies　on　WO3-X　played　a　more　important　role　in　the　separation　of　photogenerated　electron-hole　pairs　and　improvement　of　the　photocatalytic　activity　than　the　bulk　defects.　These　results　indicated　that　controlling　of　the　number　and　types　of　oxygen　vacancies　on　WO3　is　important　to　obtain　high-performance　WO3-X　photocatalysts.