With　ideal　metal　utilization　efficiency　and　homogeneous　active　sites,　single　atom　catalysts　(SACs)　have　attracted　extensive　attention　in　heterogeneous　catalysis　field.　The　performance　of　SACs　is　highly　dependent　on　the　local　coordination　environment　of　metal　single　atoms.　However,　few　works　reported　the　effect　of　surface　acidity　modification　on　the　performance　of　SACs　such　as　Pt　SACs　which　have　been　widely　studied　nowadays.　In　this　work,　a　Pt/Al2O3　SAC　has　been　successfully　prepared　using　a　bayerite　Al(OH)3　as　support　through　simple　IWI　method　for　Pt　loading.　Through　post-modification　of　Pt/Al2O3　with　acidic　WO3　and　basic　MgO,　the　surface　acidity　of　Pt/Al2O3　was　tuned.　Activity　of　CO　oxidation　and　methanol　decomposition　on　the　modified　catalysts　has　been　evaluated.　It　was　found　that　the　catalytic　performance　was　highly　related　to　the　surface　acidity　of　Pt　SACs.　Basic　MgO　modified　Pt/Al2O3　performed　better　in　CO　oxidation　under　the　reaction　condition　with　H2O.　Acidic　WO3　modified　Pt/Al2O3　showed　superior　activity　in　methanol　decomposition.　Detailed　characterization　and　in　situ　diuse　reectance　infrared　Fourier　transform　spectroscopy　(DRIFTS)　study　suggested　that　the　positive　H2O　effect　on　CO　oxidation　was　due　to　the　mitigated　formation　of　bicarbonate　species　on　Pt/Al2O3　and　WO3/Pt/Al2O3　catalysts　and　the　promoted　desorption　of　carbonate　species　from　MgO/Pt/Al2O3.　The　superior　methanol　decomposition　performance　on　WO3/Pt/Al2O3　was　owing　to　its　abundant　oxygen　vacancies　and　high　resistance　to　carbonate　accumulation.　This　study　highlights　the　importance　of　surface　acidity　modulation　of　Pt　SACs　in　heterogeneous　catalysis　and　suggests　that　fine-tuning　the　surface　acidity　can　be　an　effective　strategy　in　new　SACs　development.　©　2022　Elsevier　B.V.