Smoke　control　within　metro　tunnels　stands　as　a　pivotal　measure　in　ensuring　both　the　orderly　evacuation　and　safety　of　passengers.　This　study　investigated　the　critical　velocity　and　confinement　velocity　in　inclined　metro　tunnel　fires　via　model-scale　experiments.　The　tunnel　slope　varied　from　2　%　∼　8　%　and　four　fire　heat　release　rates　of　2.29　kW,　3.44　kW,　4.59　kW　and　5.74　kW.　Results　show　that　the　confinement　velocity　and　critical　velocity　monotonically　increase　with　the　heat　release　rate　and　tunnel　slope.　The　confinement　velocity　Vconf　was　notably　affected　by　the　equivalent　fire　source　Qu.　The　natural　exponential　function　could　effectively　express　the　relationship　between　Q*　and　Qu*,　with　the　correction　factor　of　tunnel　slope　utilized　to　adjust　the　expression.　A　new　model　for　critical　velocity　and　confinement　velocity　was　characterized　by　considering　the　tunnel　slope　and　heat　release　rate.　Comparative　results　indicated　that　the　optimizing　confinement　velocity　was　significantly　lower　than　that　defined　in　previous　studies,　while　the　proposed　critical　velocity　ratio　aligns　well　with　findings　from　prior　research.　This　study　provides　valuable　insights　into　the　design　of　smoke　control　systems　customized　for　fires　occurring　in　trains　immobilized　within　inclined　underground　tunnels.　©　2024　The　Author(s)