A　numerical　simulation　was　presented　on　the　mixed　convective　heat　transfer　of　molten　salts　in　single　side　heated　horizontal　square　tube.　The　flow　and　heat　transfer　characteristic　of　molten　salt　with　bottom,　lateral　and　top　heated　positions　were　analyzed,　respectively.　The　results　showed　that　under　non-uniform　heating　conditions,　the　velocity　profiles　of　main　core　area　changes　with　the　increase　of　flow　distance　due　to　buoyancy　effects　and　the　core　area　is　close　to　heating　surfaces.　For　different　heating　modes,　the　numbers　of　vortex　flow　formed　in　each　cross　section　of　channel　are　different.　Heat　transfer　ability　is　strengthened　due　to　the　existence　of　vortex　in　different　scales.　Good　agreement　between　simulation　results　and　mixed　convective　correlation　is　reached　and　the　deviation　between　92%　of　simulation　results　and　correlation　is　within　20%.　Under　the　same　heating　modes,　the　heat　transfer　performance　of　mixed　convection　is　strengthened　1.2-2.5　times　than　that　of　forced　convection.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.