To　analyze　the　natural　convection　heat　transfer　of　molten　salt　nanofluids　around　vertical　array　of　horizontal　cylinders,　a　numerical　simulation　is　performed　with　cylinder　numbers　in　the　range　of　N　=　2-8　and　pitches　in　the　range　of　S/D　=　5-10.　The　results　show　that　the　heat　transfer　of　nanofluids　around　each　cylinder　is　affected　by　the　position　in　the　tube　row　and　its　distance　from　the　adjacent　cylinder.　The　average　Nusselt　number　(Nu(a))　of　the　natural　convection　heat　transfer　over　the　whole　array　of　cylinders　is　determined　by　cylinder　spacing　S/D,　cylinder　number　N,　and　Ra.　When　S/D　=　5,　Nu(a)　decreases　as　the　cylinder　number　increases.　When　S/D　=　10,　Nua　increases　as　the　cylinder　number　increases.　Compared　with　the　molten　salts,　the　natural　convection　heat　transfer　of　nanofluids　is　enhanced.　This　study　provides　a　theoretical　basis　for　the　design　of　a　single-tank　energy　storage　system.