Urban　Traffic　Link　Tunnel　(UTLT)　is　a　new-type　underground　traffic　system　and　smoke　control　is　important　to　ensure　fire　safety　in　tunnels.　A　dimensionless　equation　of　back-layering　in　UTLT　tunnel　with　scaling　analysis　method　was　derived.　According　to　usual　sizes　of　UTLT,　tunnels　of　different　sizes　were　set　and　then　fire　was　simulated　with　CFD　software　FDS　5.5.　The　length　of　back-layering　was　obtained　at　different　conditions.　At　last　a　model　of　back-layering　in　UTLT　was　obtained.　The　model　agreed　well　with　full　scale　and　medium　scale　experimental　data.　The　model　of　confinement　velocity　was　derived　on　the　basis　of　back-layering　model.　The　research　can　provide　technical　reference　for　UTLT　fire　protection　design.　©　2016,　Beijing　University　of　Technology.　All　right　reserved.