Cross　-passage　is　a　commonly　encountered　structure　within　metro　tunnels,　providing　a　swift　route　for　evacuating　personnel　from　the　accident　tunnel　to　the　safe　tunnel　opposite.　Ventilation　in　the　cross　-passage　of　metro　tunnels　is　established　through　the　collaborative　operation　of　ventilation　systems　on　both　sides　of　the　tunnel.　Concurrently,　smoke　movement　within　the　metro　tunnel　is　impacted　by　factors　such　as　train　blockage　and　the　accumulation　of　heat　within　the　train　carriages.　The　former　correlations　need　further　refinement　to　predict　the　critical　velocity　and　driving　force　required　to　prevent　smoke　from　spreading　into　a　metro　tunnel　cross　-passage.　Onedimensional　theoretical　analysis　and　full-scale　cold　smoke　experiments　were　performed　to　investigate　the　relationship　between　the　air　supply　parameters　of　tunnel　fans　on　both　sides　and　the　ventilation　velocity　in　the　crosspassage.　A　calculation　model　of　fan　type　selection　in　the　opposite　side　safe　tunnel　for　smoke　control　in　the　tunnel　cross　-passage　is　proposed.　The　influence　of　train　location,　fire　heat　release　rate,　and　main　tunnel　ventilation　velocity　on　critical　velocity　in　the　cross　-passage　was　quantified　by　numerical　simulations.　The　results　show　that　the　critical　velocity　in　the　cross　-passage　under　unobstructed　conditions　surpasses　that　under　blocked　conditions.　Meanwhile,　the　critical　velocity　exhibits　relative　stability　under　both　unobstructed　and　blocked　conditions.　On　the　basis　of　the　dimensionless　analysis,　a　piecewise　function　was　proposed　to　predict　the　critical　velocity　in　tunnel　cross　-passage.　The　outcomes　of　this　study　provide　valuable　guidance　for　the　implementation　of　fire　prevention　and　smoke　control　measures　in　tunnels　with　similar　structures.