A　method　for　calculating　dynamic　characteristics　of　stepped　labyrinth　seals　with　consideration　of　inlet　preswirl　is　proposed　to　solve　the　problem　that　the　dynamic　characteristics　of　stepped　labyrinth　seals　are　affected　by　inlet　preswirl.　Governing　equations　of　air　excitation　force-rotor　displacement-rotor　velocity　are　established　based　on　Murphy＇s　small　displacement　vorticity　principle.　CFD　numerical　simulation　method　is　used　to　calculate　the　flow　passage　of　full-ring　seals　with　different　prswirl　ratios.　Dynamic　characteristic　parameters　such　as　stiffness　and　damping　are　obtained　by　solving　the　governing　equations　in　the　frequency　domain.　The　dynamic　characteristics　of　stepped　labyrinth　seals　with　different　preswirl　ratios　are　studied.　The　flow　field　characteristics　of　stepped　labyrinth　seal　are　studied　by　drawing　the　pressure　distribution　and　velocity　vector　diagrams　in　the　flow　passage.　Numerical　simulation　results　show　that　with　the　increase　of　preswirl　ratio,　the　direct　stiffness　increases　at　low　frequency　and　decreases　at　high　frequency,　the　cross　stiffness　is　almost　constant,　and　the　cross　damping　decreases　with　the　increase　of　preswirl.　Air　flow　preswirl　significantly　reduces　the　direct　damping,　and　the　estimated　direct　damping　in　preswirl　ratio　λ=0.255　and　λ=0.516　conditions　decreases　by　16.9%　and　21.4%　on　average　compared　with　the　case　of　λ=0　condition.　With　the　increase　of　throttling　times,　the　pressure　drop　of　airflow　passing　through　the　sealing　tooth　increases　gradually,　which　are　0.25　MPa,　0.374　MPa　and　0.499　MPa,　respectively.　The　velocity　of　sealing　tooth　tip　also　increases　gradually,　which　are　79.5　m/s,　88.36　m/s　and　106.0　m/s,　respectively.　The　step　arrangement　of　sealing　teeth　increases　the　complexity　of　the　main　flow　passage,　and　the　step　sealing　flow　passage　is　divided　into　throttling　region,　jet　region　and　eddy　region.　The　eddy　region　has　two　vortexes　with　opposite　direction,　which　increase　the　dissipation　of　airflow　kinetic　energy　in　the　flow　passage.　©　2022,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.