—Utility　tunnels　are　widely　built　in　many　cities.　When　an　unexpected　fire　occurs　in　the　electrical　compartment　of　utility　tunnel,　the　smoke　temperature　below　the　utility　tunnel　ceiling　is　one　of　the　most　important　factors　for　thermal　detection　and　alarm.　In　this　paper,　the　smoke　temperature　distribution　under　the　longitudinal　ventilation　in　a　utility　tunnel　fire　accident　is　studied　by　combining　experiment　and　numerical　simulation.　The　main　purpose　of　this　paper　is　to　study　the　smoke　temperature　distribution　below　the　ceiling　under　the　effect　of　longitudinal　ventilation　in　a　utility　tunnel,　and　provide　guidance　for　the　installation　of　detector　in　case　of　fire.　In　addition,　three　important　factors　such　as　ventilation　velocity,　heat　release　rate　and　vertical　position　of　fire　source　are　considered　respectively.　The　thermocouple　trees　are　used　to　measure　the　temperature　along　the　longitudinal　direction　of　utility　tunnel.　Results　show　that　the　maximum　temperature　of　the　utility　tunnel　is　directly　above　the　fire　source　without　longitudinal　ventilation.　What’s　more,　with　the　ventilation　velocity　increases,　the　maximum　temperature　below　the　ceiling　gradually　moves　to　the　downstream　of　the　fire　source　in　utility　tunnel.　Finally,　a　new　correlation　formula　is　proposed　to　predict　the　temperature　distribution　of　smoke　in　utility　tunnels　on　the　basis　of　theoretical　analysis.　The　longitudinal　temperature　distribution　obtained　by　numerical　simulation　is　in　good　agreement　with　the　experimental　tests.　Therefore,　the　research　in　this　paper　is　helpful　to　prevent　utility　tunnel　fire　and　reduce　people＇s　property　loss.　©　2020,　International　Association　of　Engineers.　All　rights　reserved.