Pt/CeO2　were　synthesized　through　the　polyvinyl　alcohol　(PVA)　reduction　protection　method,　and　the　efficacies　of　the　catalysts　for　water　gas　shift　(WGS)　reaction　were　evaluated.　Pt　was　deposited　on　CeO2　in　different　forms　of　Pt　single　atoms　(0.15Pt1/CeO2)　and　Pt　nanoparticles　(0.56Pt/CeO2),　respectively.　CO　conversion　(400　degrees　C)　and　turnover　frequency　(TOF)　(250　degrees　C)　of　the　Pt　single　atom　catalyst　0.15Pt1/CeO2　were　89%　and　0.85　s-1,　respectively,　significantly　higher　than　that　of　the　Pt　nanoparticle　catalyst　0.56Pt/CeO2　for　the　WGS　reaction.　The　superior　catalytic　performance　Pt　single　atom　catalyst　can　be　attributed　to　enhanced　low-temperature　reducibility　and　increased　oxygen　vacancies　facilitated.　In-situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　(in-DRIFTS)　revealed　that　Pt　single　atoms　promoted　the　creation　of　oxygen　vacancies　on　CeO2,　which　dissociated　H2O　to　H2　and　adsorbed　O,　that　subsequently　interacted　with　the　weakly　adsorbed　CO　on　these　Pt　sites　to　generate　CO2.　In　contrast,　the　adsorption　strength　of　CO　nanoparticles　Pt　was　much　higher.　CO　reacted　with　the　OH　groups　on　the　Pt　nanoparticle　catalyst　surface　to　form　formate　species,　which　then　decomposed　to　produce　both　CO2　and　H2.　This　study　presents　a　promising　strategy　for　designing　highly　efficient　catalysts　tailored　for　WGS.