The　previous　researchs　of　the　critical　velocity　are　mainly　for　single-point　tunnel　and　limited　for　branched　tunnel.　The　critical　velocity　together　with　the　driving　force　for　preventing　smoke　backflow　in　branched　tunnel　cannot　be　precisely　predicted　by　former　correlations.　Experiments　are　conducted　in　this　work　to　investigate　the　fire-induced　smoke　movement　in　branched　tunnel　under　the　cases　of　critical　ventilation　velocity　condition.　The　pressure　change　in　branched　tunnel　is　analyzed　on　the　basis　of　one　dimensional　theory,　and　the　fire　source　and　bifurcation　angle　was　taken　into　account.　Results　show　that　the　bifurcation　angle　has　a　significant　influence　on　the　critical　velocity　and　the　driving　force　for　preventing　smoke　backlayering　due　to　the　local　resistance.　The　pressure　difference　due　to　the　plume　blockage　created　by　the　fire　are　expressed　on　the　basis　of　experimental　data.　Based　on　the　theoretical　analysis　of　pressure　change,　new　relatively　correlations　considering　the　bifurcation　angle　and　heat　release　rate　are　proposed　to　predict　the　critical　velocity　together　with　the　required　pressure　rise　for　preventing　smoke　backflow　in　branched　tunnel.　The　predicted　critical　velocity　by　proposed　model　are　found　to　comply　well　with　the　experimental　data.