Increasing　attention　has　been　paid　to　the　axial-flow　turbine　in　supercritical　CO2　power　cycle　and　the　tip　leakage　has　a　significant　effect　on　turbine　performance.　In　the　absence　of　investigation　into　supercritical　CO2　seal　on　shroud,　four　types　of　configurations　are　established　based　on　a　supercritical　CO2　axial-flow　turbine:　the　structure　without　leakage　(Without　leakage)　and　the　structures　with　a　smooth　leakage　passage　(Smooth),　labyrinth　seals　(Labyrinth)　and　dry　gas　seal　(DGS).　The　flow　characteristics　and　aerodynamic　performance　are　discussed　in　detail.　The　dry　gas　seal　arranged　on　the　shroud　can　substantially　improve　the　overall　performance.　Compared　with　Labyrinth,　the　leakage　of　DGS　is　reduced　by　99.38%　while　the　power　and　isentropic　efficiency　are　raised　by　0.88%　and　1.56%　respectively.　The　mass　flow　rate　and　leakage　increase　while　the　power　and　isentropic　efficiency　decrease　as　seal　clearance　increases.　The　mechanical　load　and　thermal　load　result　in　converse　axial　deformation　of　seal　end　face　while　the　former　performs　more　remarkably.　DGS　achieves　notable　performance　close　to　Without　leakage　under　different　inlet　pressure　and　temperature.　©　2020　Elsevier　Ltd