A　non-axisymmetric　endwall　contour　optimization　design　system　combined　with　Kriging　Surrogate　model,　NSGA-II　algorithms　and　numerical　evaluation　method　was　established.　Multi-objective　optimization　on　the　turbine　cascade　non-axisymmetric　endwall　contour　with　upstream　slot　coolant　jet　for　maximizing　the　endwall　cooling　and　blade　phantom　cooling　was　conducted.　The　cooling　performance　was　compared　and　analyzed　between　the　optimized　non-axisymmetric　endwall　and　the　referenced　endwall　under　different　preswirl　ratios.　The　optimization　results　show　that　the　averaged　endwall　cooling　effectiveness　of　the　optimal　design　scheme　1　for　maximizing　endwall　cooling　effectiveness　and　the　optimal　design　scheme　2　considering　the　tradeoff　between　endwall　cooling　effectiveness　and　blade　phantom　cooling　effectiveness　was　increased　by　3.52%　and　2.18%,　respectively,　compared　with　the　referenced　design.　The　coolant　coverage　on　the　pressure-side　non-axisymmetric　contoured　endwall　increases　notably.　The　non-axisymmetric　endwall　contour　decreases　the　blade　phantom　cooling　effectiveness　due　to　suppressed　secondary　flow　vortex.　The　non-axisymmetric　endwall　changes　the　location　of　the　high　heat　transfer　regions　as　a　result　of　the　variation　of　passage　vortex.　The　optimal　design　schemes　1　and　2　can　increase　the　pressure-side　endwall　cooling　effectiveness　under　slot　coolant　mass　flow　ratio　of　1.0%　and　preswirl　ratio　of　0.6.　When　the　slot　coolant　mass　flow　ratio　equals　1.5%,　the　pressure-side　endwall　convex　enlarges　the　coolant　coverage,　but　the　averaged　cooling　effectiveness　of　the　front　endwall　is　decreased　under　the　influence　of　slot　preswirl　jet　flow.　©　2021,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.