The　power　cable　fire　in　an　utility　tunnel　is　difficult　to　control　due　to　its　characteristics　of　narrow　and　long　structure,　cable　layer　arrangement,　and　variable　fire　locations.　Water　mist　system　is　one　of　commonly　used　method　for　fire　control.　This　paper　studied　the　fire　extinguishing　efficiency　of　high-pressure　water　mist　system　in　utility　tunnel　by　large　eddy　simulation　(LES).　In　order　to　compare　the　fire　extinguishing　effect　of　the　water　mist　system,　two　working　conditions　are　designed,　that　is,　the　utility　tunnel　with　water　mist　system　and　without　water　mist　system.　Results　have　shown　that　continuously　operating　of　high-pressure　water　mist　system　can　extinguish　cable　fires　effectively.　The　cooling　effect　of　the　water　mist　is　obvious　and　it　can　control　fire　development　or　extinguished　fire.　The　temperature　of　utility　tunnel　would　be　reduced　so　as　to　prevent　the　structure　from　being　destroyed.　©　2023　Institute　of　Physics　Publishing.　All　rights　reserved.