Urban　underground　tunnels　usually　have　lager　traffic　volumes　and　complex　structures　comparing　with　other　kinds　of　tunnel.　This　can　give　higher　fire　risk　and　also　make　smoke　control　to　become　more　difficult　once　the　fire　occurs.　The　effect　of　the　fire　size　and　intersection　angle　on　the　smoke　spread　and　smoke　mass　flow　distribution　in　underground　urban　tunnel　with　horizontal　junctions　are　studied　by　the　numerical　simulation　in　this　paper.　The　results　show　that　the　power　size　can　affect　the　smoke　spread　heavily,　but　it　has　little　effect　on　the　smoke　mass　flow　distributions　between　the　downstream　main　tunnel　and　the　branch　tunnels.　Variation　of　the　intersection　angle　almost　have　an　effect　on　the　smoke　spread　in　upstream　main　tunnel,　but　its　effect　on　the　smoke　spread　and　smoke　mass　flow　distributions　in　branch　tunnel　cannot　be　neglect.　The　results　are　expected　to　be　useful　for　the　smoke　control　system　design　in　these　kinds　of　tunnels.　(C)　2014　The　Authors.　Published　by　Elsevier　Ltd.