The　flow　and　heat　transfer　characteristics　of　air/mist　coolant　in　non-rotating　ribbed　two-pass　rectangular　channel　were　numerically　investigated　with　SST　turbulence　model.　The　effect　of　mist　initial　diameter　and　mist　initial　mass　concentration　on　the　mist/air　cooling　parameters　was　analyzed.　Three　kinds　of　coolants,　mist/air,　air　and　steam,　were　comparatively　discussed　for　the　heat　transfer　performance.　The　results　show　that　the　mist　flow　distance　increases　with　increasing　mist　initial　diameter　and　there　exists　an　optimum　mist　diameter;　the　mist　flow　distance,　the　averaged　channel　Nusselt　number,　the　flow　resistance　and　the　thermal　performance　factor　increase　with　the　mist　initial　mass　concentration.　For　the　case　of　Re=40　000,　the　averaged　channel　Nusselt　number　of　mist/air　increases　by　8.6%　and　25.39%　compared　with　steam　and　air　respectively,　and　that　of　the　thermal　performance　factor　increases　by　6.58%　and　23.47%.　©,　2015,　Xi＇an　Jiaotong　University.　All　right　reserved.