This　paper　presents　a　numerical　investigation　on　the　steady　and　unsteady　flow　characteristics　of　rim　seal　for　the　first　stage　in　gas　turbine.　The　Reynolds-averaged　Navier-Stokes　equations,　coupled　with　shear　stress　transport　turbulence　model,　and　a　scalar　equation　are　solved.　In　the　steady-state　conditions,　the　influences　of　rim　seal　structures　and　rotational　speeds　on　the　sealing　effectiveness　and　non-dimensional　sealing　air　mass　flow　have　been　numerically　investigated.　In　the　unsteady-state　conditions,　the　pressure　distribution,　pressure-frequency　and　sealing　effectiveness　are　discussed　in　detail.　The　results　obtained　in　this　study　indicate　that　the　sealing　effectiveness　increases　with　the　non-dimensional　sealing　air　mass　flow.　The　minimum　non-dimensional　sealing　mass　flow　for　the　axial　rim　seals　and　radial　seals　ranges　from　9.62×103to　9.63×103and　from　5.07×103to　5.75×103,　respectively.　It　means　that　the　radial　seals　perform　better　than　the　axial　ones　in　sealing　effectiveness.　The　minimum　non-dimensional　sealing　mass　flow　increases　with　the　increase　of　rotational　speeds.　The　increase　of　sealing　air　is　conducive　to　reducing　instability　in　the　rim　seal　cavity,　which　has　small　influences　on　the　circumferential　pressure　downstream　the　vane　trailing　edge.　The　unsteady-state　sealing　effectiveness　is　lower　than　that　calculated　in　steady　state.　©　2017　Chin.　Soc.　for　Elec.　Eng.