The　selective　conversion　of　ethane　(C2H6)　to　ethylene　(C2H4)　under　mild　conditions　is　highly　wanted,　yet　very　challenging.　Herein,　it　is　demonstrated　that　a　Pt/WO3-x　catalyst,　constructed　by　supporting　ultrafine　Pt　nanoparticles　on　the　surface　of　oxygen-deficient　tungsten　oxide　(WO3-x)　nanoplates,　is　efficient　and　reusable　for　photocatalytic　C2H6　dehydrogenation　to　produce　C2H4　with　high　selectivity.　Specifically,　under　pure　light　irradiation,　the　optimized　Pt/WO3-x　photocatalyst　exhibits　C2H4　and　H2　yield　rates　of　291.8　and　373.4　mu　mol　g-1　h-1,　respectively,　coupled　with　a　small　formation　of　CO　(85.2　mu　mol　g-1　h-1)　and　CH4　(19.0　mu　mol　g-1　h-1),　corresponding　to　a　high　C2H4　selectivity　of　84.9%.　Experimental　and　theoretical　studies　reveal　that　the　vacancy-rich　WO3-x　catalyst　enables　broad　optical　harvesting　to　generate　charge　carriers　by　light　for　working　the　redox　reactions.　Meanwhile,　the　Pt　cocatalyst　reinforces　adsorption　of　C2H6,　desorption　of　key　reaction　species,　and　separation　and　migration　of　light-induced　charges　to　promote　the　dehydrogenation　reaction　with　high　productivity　and　selectivity.　In　situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　and　density　functional　theory　calculation　expose　the　key　intermediates　formed　on　the　Pt/WO3-x　catalyst　during　the　reaction,　which　permits　the　construction　of　the　possible　C2H6　dehydrogenation　mechanism.　The　Pt/WO3-x　photocatalyst　consisted　of　ultrafine　Pt　nanoparticles　supported　on　the　surface　of　oxygen-defective　tungsten　oxide　nanoplates　manifests　high　activity　and　fine　reusability　for　selective　ethylene　formation　from　ethane　dehydrogenation　by　simulated　sunlight　under　mild　conditions.　image