The　defect-rich　ultrathin　WO3　nanosheets　are　successfully　prepared　as　photocatalysts　via　heating　treatment　for　the　pristine　WO3　nanosheets　(NS)　in　vacuum　(NSV)　and　N-2　atmosphere　(NSN).　The　increment　of　degradation　efficiencies　of　levofloxacin　(LVX)　over　NS　(49.9　%)　＜NSN　(75.9　%)　＜NSV　(84.3　%)　under　visible　light　is　mainly　due　to　the　increase　of　oxygen　vacancies　(O-VS).　These　OVS　have　the　potential　to　generate　more　unsaturated　W　centers　(Lewis　acid　sites)　which　are　beneficial　to　activate　the　C=O　of　carboxyl　and　the　C-N　of　piperazinyl　in　LVX　molecules　via　(WO)-O-center　dot　center　dot　center　dot=C　and　(WN)-N-center　dot　center　dot　center　dot-C　coordination.　LC-MS　result　further　demonstrates　that　the　LVX　molecules　breakdown　are　mainly　initiated　by　cleaving　the　activated　C=O　and　C-N　bonds.　More　O-VS　can　adsorb　and　activate　more　O-2　molecules　which　shall　be　converted　to　center　dot　O-2(-)　by　photogenerated　electron.　The　photogenerated　holes　are　transferred　on　the　catalysts　surface　to　form　center　dot　OH　via　oxidizing　water　or　directly　degrade　the　activated　LVX　molecules.　Finally,　a　possible　mechanism　is　proposed　to　understand　the　pathway　for　photocatalytic　degradation　LVX　at　molecular　scale.　This　study　highlights　the　significant　role　of　coordination　activation　for　the　photocatalytic　degradation　of　antibiotics.