Due　to　rainfall,　the　soil-rock　differential　weathering　interface　of　spherical　weathered　granite　soil　slopes　is　prone　to　evolve　into　a　dominant　seepage　channel　and　undergo　seepage　suffosion,　which　accelerates　the　deformation　and　instability　of　these　slopes.　However,　little　research　has　been　carried　out　on　the　characteristics　of　seepage　suffosion　and　the　migration　of　fine　particles.　Based　on　the　unsaturated　seepage　theory　of　porous　media,　a　numerical　calculation　framework　is　established　to　accurately　describe　the　seepage　suffosion　process　at　the　soil-rock　interface,　considering　the　coupling　relationship　between　the　fine　particle　migration,　suffosion　initiation　response　and　unsaturated　seepage.　The　finite　element　method　is　used　to　construct　a　seepage　suffosion　model　for　unsaturated　granite　residual　soil　under　the　effect　of　dominant　flow.　Based　on　the　seepage　suffosion　process　of　homogeneous　soil　columns,　the　suffosion　characteristics　of　dominant　flow　under　three　typical　soil-rock　interface　burial　states　are　systematically　investigated.　The　results　show　that　the　soil-rock　interface　and　the　matrix　permeability　of　spherical　weathered　granite　soil　slopes　are　highly　variable,　with　the　wetting　front　forming　a　downward　depression　infiltration　funnel,　and　the　degree　of　depression　of　the　wetting　front　becomes　more　pronounced　as　rainfall　continues.　The　degree　of　fine　particle　loss　is　related　to　the　burial　state　of　the　soil-rock　interface,　in　which　the　dominant　flow　potential　suffosion　of　the　under-filled　soil　condition　is　the　most　significant,　and　even　excess　pore　water　pressure　occurs　at　the　interface,　which　is　the　most　unfavorable　to　the　stability　of　this　type　of　slope.　The　research　results　can　provide　a　scientific　basis　for　accurately　evaluating　the　stability　of　spherical　weathered　granite　soil　slopes　under　rainfall　conditions.　©　2024　Biodiversity　Research　Center　Academia　Sinica.　All　rights　reserved.