In　order　to　obtain　the　laminar　natural　convection　heat　transfer　mechanism　of　molten　salt　from　vertical　array　of　heated　horizontal　cylinders,　the　natural　convection　heat　transfer　of　molten　salt　around　horizontal　cylinders　with　different　diameters　was　studied　by　simulation.　The　result　shows　that　the　natural　convective　heat　transfer　of　molten　salt　around　lower　cylinder　remains　the　same　as　that　from　a　single　cylinder.　However,　the　heat　transfer　characteristics　of　the　upper　cylinder　are　great　influenced　by　the　presence　of　the　lower　cylinder.　The　Nusselt　number　of　the　upper　cylinder　was　influenced　by　the　lower　cylinder　by　two　opposing　effects.　At　a　small　S/D　ratio,　the　driving　force　for　heat　transfer　from　the　upper　cylinder　is　lower　than　that　for　the　lower　cylinder　due　to　the　preheating　of　the　fluid　above　its　free　stream　value　by　the　lower-cylinder,　it　makes　the　NuU　smaller;　At　a　large　S/D　ratio,　due　to　the　plume　rising　from　the　lower　cylinder,　the　upper　cylinder　experiences　effectively　a　mixed　convection　regime,　its　own　buoyancy-　induced　flow　augmented　by　the　plume　of　the　lower　cylinder,　this　makes　the　NuU　bigger.　The　paper　proposes　correlation-equations　for　natural　convection　heat　transfer　of　LiNO3　from　horizontal　cylinders　set　in　a　vertical　array,　this　study　is　very　important　for　the　design　of　heat　exchanger　with　thermal　storage　of　molten　salt.　©　2016,　Editorial　Board　of　Acta　Energiae　Solaris　Sinica.　All　right　reserved.