In　order　to　further　increase　the　gas　turbine　efficiency　by　increasing　the　turbine　inlet　temperature,　an　advanced　cooling　technology　needs　to　be　developed.　Recently,　mist　/steam　(air)　cooling　is　considered　as　a　promising　technology　to　effectively　cool　the　hot　components　such　as　gas　turbine　vanes　and　blades.　A　series　of　experimental　investigations　and　numerical　simulations　conducted　in　the　past　proved　the　feasibility　and　superiority　of　mist　cooling　technology　in　elevated　gas　turbine　working　condition.　The　aim　of　this　study　is　to　numerically　analyze　the　secondary　flow　structure　and　the　influence　of　secondary　flow　distribution　on　heat　transfer　in　steam　and　mist/steam　cooling　channels　with　different　rib　angles　by　using　vortex　core　interaction.　In　addition,　the　heat　transfer　characteristics　of　steam　and　mist/steam　in　gas　turbine　cooling　channels　with　rib　angles　of　30,　45,　60,　90,　duct　aspect　ratio　2:1,　Reynolds　number　ranging　from　10000　to　60000　and　mist　ratio　increasing　from　2%　to　8%　are　also　investigated.　The　commercial　software　ANSYS　CFX　14.5　is　used　to　solve　the　3-D　steady　Reynolds-averaged　Navier-Stokes　equations　with　a　SST　turbulent　model.　The　numerical　results　of　Nusselt　number　(Nu)　distribution　along　the　centerline　of　each　channel　with　steam-only　are　validated　with　the　experimental　values.　Numerical　results　indicate　that　the　predicted　results　are　in　good　agreement　with　the　experimental　data.　The　distribution　and　strength　of　longitudinal　secondary　flows　in　30,　45,　60　ribbed　channels　and　transverse　secondary　flows　in　90　ribbed　channel　have　a　great　influence　on　the　distribution　of　Nusselt　number.　The　averaged　Nu　in　30,　45,　60　ribbed　channels　is　higher　than　that　in　90　ribbed　channel　due　to　longitudinal　secondary　flow　having　a　better　heat　transfer　performance　than　transverse　secondary　flow.　The　decrease　of　averaged　Nu　between　two　neighbored　ribs　along　inclined　ribs　is　mainly　induced　by　the　decreased　strength　of　longitudinal　secondary　flow　along　the　same　direction　in　30,　45,　60　ribbed　channels.　The　averaged　Nu　of　mist/steam　with　5%　mist　injection　in　the　four　channels　increases　by　97.98%-151.9%　compared　with　steam　at　Re=60000.　Furthermore,　the　averaged　Nu　increases　by　about　11.08%　to　213.6%　compared　with　steam,　when　the　mist　ratio　increases　from　2%　to　8%.　The　60　ribbed　channel　achieves　the　best　heat　transfer　performance　in　mist/steam　cooling　channels.