There　has　been　an　increasing　attention　on　single-tank　thermal　energy　storage,　attracted　by　the　low　cost,　high　efficiency　and　compactness　in　the　operation.　The　most　researches　on　single-tank　thermal　energy　storage　focused　on　temperature　stratification　to　improve　its　heat　discharging　efficiency　using　water　as　heat　storage　media.　The　present　research　aims　at　investigating　heat　discharging　performance　by　improving　natural　convection　heat　transfer　of　molten　sat　around　coil　heat　exchanger　in　single　heat　storage　tank.　The　effect　of　different　parameters　of　the　coil　heat　exchanger　on　the　heat　discharging　performance,　flow　field　and　temperature　distribution　are　analyzed　and　discussed　in　the　single　molten　salt　tank.　The　results　show　that　the　heat　discharging　performance　of　the　coil　heat　exchanger　can　be　enhanced　by　increasing　the　buoyancy-driven　flow　around　the　coil　heat　exchanger.　The　heat　discharging　efficiency　can　be　improved　by　the　optimal　arrangement　of　coil　heat　exchanger　for　the　highest　velocity　can　be　induced　around　it,　which　results　in　a　fully　mixed　of　molten　salts　and　its　temperature　turns　to　uniform,　instead　of　temperature　stratification.　Based　on　the　results,　a　correlation　among　the　natural　convection　Nu　number　with　Ra　number　and　other　heat　exchanger　parameters　in　a　single　molten　salt　tank　is　obtained　by　numerical　results.　The　research　results　provide　a　theoretical　basis　and　paradigm　for　the　design　of　single　thermal　storage　tank　energy　storage　system.