The　gamma-WO3(001)　surfaces　doped　by　a　series　of　group　VB　elements　have　been　investigated　by　means　of　first-principles　density　functional　theory　(DFT)　calculations　doping　of　VB　element　is　preferential　under　O-rich　growth　conditions　and　that　the　replacement　of　tungsten　by　Ta　atom　is　energetically　favorable　among　three　group　VB　elements.　The　introduction　of　a　group　VB　atom　into　the　surface　results　in　the　downward　shift　of　the　Fermi　level,　and　in　most　cases,　the　2p　states　derived　from　the　in-plane　oxygen　atom　are　still　the　dominate　components　at　the　Fermi　level　as　before　doping.　However,　the　substitution　of　Ta　dopant　for　6-fold-coordinated　tungsten　atom　(W-6f)　at　the　top　layer　is　a　special　case　in　which　the　2p　states　of　the　top　terminal　oxygen　atom　just　above　Ta　become　the　primary　compositions　at　the　Fermi　level.　Only　in　this　model,　the　spin　densities　are　mainly　located　on　the　terminal　oxygen　atoms　near　the　Ta　site,　and　the　oxygen　radical　center　observed　in　the　gas-phase　W3O9+　cluster　is　reproduced.　Therefore,　the　formation　of　radical　oxygen　center　in　the　condensed　phase　depends　on　not　only　the　substituent　site　but　also　the　type　of　the　dopant.　Moreover,　additional　calculations　are　performed　to　study　the　oxidation　reaction　of　CO　molecule　on　the　above　Ta　doped　surface,　and　results　indicate　that　the　energy　barrier　for　CO　oxidization　is　obviously　reduced　compared　to　the　undoped　one,　which　implies　that　the　introduction　of　Ta　at　W-6f　site　can　efficiently　improve　the　oxidation　reactivity　of　the　WO3(001)　surface.