With　the　continuous　increase　of　aerodynamic　and　thermal　load,　the　endwall　of　modern　gas　turbines　has　become　the　critical　region　affected　by　the　uncertainties　in　the　manufacturing　and　operation　process　and　thus　is　very　likely　to　suffer　performance　degradation　and　thermal　failure.　Therefore,　it　is　critical　to　understand　and　quantify　the　impacts　of　uncertainty　factors　on　endwall　aero-thermal　performance.　Based　on　Kriging　surrogate,　the　frameworks　of　uncertainty　quantification　and　global　sensitivity　analysis　are　constructed　for　a　gas　turbine　blade　endwall.　The　impacts　of　slot　geometry　deviations　(slot　width,　endwall　misalignment)　and　mainstream　condition　fluctuations　(turbulence　intensity,　inlet　flow　angle)　on　endwall　aero-thermal　performance　are　quantified　and　analyzed.　Results　show　that　the　actual　performance　of　the　endwall　has　a　high　probability　of　deviating　from　its　nominal　value.　With　respect　to　the　nominal　values,　the　maximum　deviations　of　aerodynamic　losses,　averaged　film　cooling　effectiveness　and　averaged　Nusselt　number　reach　up　to　0.33%,　45%　and　5.0%,　respectively.　The　critical　regions　which　are　most　sensitive　to　the　input　uncertainty　parameters　are　identified.　Furthermore,　the　inlet　flow　angle　is　proved　to　be　the　most　significant　parameter　affecting　the　endwall　aero-thermal　performance　through　sensitivity　analysis.　The　influence　mechanisms　of　the　inlet　flow　angle　on　endwall　aero-thermal　performance　are　clarified　by　detailed　flow　and　thermal　field　analysis.　Results　show　that　the　inlet　flow　angle　significantly　alters　the　size　and　strength　of　the　secondary　flow　structures,　resulting　in　a　large　variation　of　endwall　aero-thermal　performance.　Quantitatively,　a　positive　incidence　angle　of　2　degrees　can　lead　to　a　0.1%　reduction　of　total　pressure　coefficient,　a　12%　reduction　of　averaged　film　cooling　effectiveness　and　a　2%　enhancement　of　averaged　Nusselt　number.　Copyright　©　2020　ASME.