The　three-dimensional　steady　Reynolds-Averaged　Navier-Stokes　(RANS)　equation　and　the　Spalart-Allmaras　turbulence　model　are　used　to　investigate　the　high　speed　over-tip　leakage　flow　in　a　transonic　turbine　stage.　Moreover,　the　influence　of　inlet　turbulence　intensity　on　heat　transfer　characteristics　of　top　flows　is　investigated.　The　turbulence　model　is　validated　by　a　comparison　with　experimental　data.　Numerical　results　show　that　the　blade　tip　attains　the　maximum　heat　transfer　coefficient　and　the　tip　leakage　flow　is　subsonic　(0.3＜Ma＜0.8)　when　the　tip　clearance　is　small　(s=0.188%L).　When　the　blade　tip　clearance　increases　to　0.75%　of　the　moving　blade　height　(L),　the　supersonic　region　enlarges　towards　the　leading　edge.　The　heat　transfer　coefficient　on　blade　tip　increases　firstly,　and　then　decreases　as　the　tip　clearance　height　increases.　The　minimum　heat　transfer　coefficient　on　blade　tip　is　obtained　in　the　case　s=0.75%L,　and　the　leakage　flow　is　supersonic　(1.0＜Ma＜1.3)　in　the　clearance　gap.　The　heat　transfer　coefficient　near　the　leading　edge　is　significantly　affected　by　the　motion　of　the　horse　vortex　with　the　increase　of　tip　clearance　height.　Inlet　turbulence　intensity　has　little　effect　on　the　blade　tip　heat　transfer　performance　due　to　the　sharp　acceleration　of　the　leakage　flow.　However,　it　is　observed　that　the　cross-passage　secondary　flow　near　the　leading　edge　is　weakened　with　high　inlet　turbulence　intensity.　©　2016,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.