In　order　to　reduce　the　large　tip　leakage　flow　loss　of　turbine　stage,　a　design　scheme　of　blade　tip　labyrinth　brush　seal　instead　of　traditional　tip　labyrinth　seal　is　proposed　to　decrease　the　tip　leakage　flow　rate　and　improve　the　aerodynamic　efficiency.　The　leakage　flow　rate　of　the　experimental　labyrinth　brush　seal　is　predicted　using　the　Reynolds-averaged　Navier-Stokes　solution　based　on　the　non-linear　Darcian　porous　medium　model.　The　numerically　predicted　leakage　flow　rate　well　agrees　with　the　experimental　measurements,　validating　the　reliability　of　the　presented　numerical　method.　The　first　and　last　long　teeth　of　the　labyrinth　seal　are　designed　to　bristle　packs　named　as　the　preposed　and　postposed　labyrinth　brush　seals　based　on　the　1.5　turbine　stage.　The　tip　leakage　flow　and　aerodynamic　performance　of　the　1.5　turbine　stage　with　two　kinds　of　labyrinth　brush　seals　at　the　bristle　clearance　from　0　mm　to　0.4　mm　are　compared　and　analyzed.　Numerical　results　show　that　similar　tip　leakage　flow　rate　and　aerodynamic　efficiency　for　two　kinds　of　labyrinth　brush　seals　at　the　same　bristle　clearance　are　obtained.　The　leakage　flow　rate　of　the　labyrinth　brush　seal　with　a　bristle　clearance　of　0.4　mm　is　decreased　by　18%　in　comparison　with　the　blade　tip　labyrinth　seal,　and　the　aerodynamic　efficiency　is　increased　by　0.6%.　The　blade　tip　seal　clearance　loss　mostly　includes　cavity　diffusion　loss　and　exit　cavity　viscosity　loss.　Compared　with　the　labyrinth　seal　structure,　the　labyrinth　brush　seal　structure　can　decrease　the　relative　deflection　angle　of　exit　flow.　This　flow　behavior　results　in　decreasing　the　mixing　loss　between　the　tip　leakage　flow　and　mainstream.　This　paper　reveals　the　mechanism　of　using　blade　tip　labyrinth　brush　seal　to　improve　the　aerodynamic　efficiency　of　turbine　stage　through　decreasing　exit　cavity　viscosity　loss.　This　work　may　provide　theoretical　basis　and　technical　support　for　the　brush　seal　application　in　turbomachinery.　©　2019,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.