More　than　30,000　tons　of　molten　salts　as　efficient　heat　transfer　and　thermal　energy　storage　materials　have　been　employed　in　a　single　commercial　concentrating　solar　power　plant.　Nanoparticles　could　increase　the　thermal　performance　of　molten　salts.　However,　there　is　no　efficient　synthesis　method　for　the　mass　production　of　molten　salt　nanofluids　by　far.　In　this　work,　two　techniques　that　are　aqueous　solution　and　high-temperature　melting　methods,　which　could　be　potentially　used　for　the　large　scale　production　of　molten　salt　nanofluids,　were　comparatively　evaluated　by　investigating　the　thermal　performance　of　solar　salt　dispersed　with　1.0　wt　%　20　nm　SiO2　nanoparticles.　The　differential　scanning　calorimetry,　thermogravimetric　analysis,　and　laser　flash　analysis　were　employed　to　analyze　the　thermal　performance　of　molten　salt　nanofluids.　Results　showed　that　the　high-temperature　melting　method　achieved　an　energy-efficient　and　much-simplified　synthesis　process,　which　was　superior　to　the　aqueous　solution　method　for　the　mass　production　of　molten　salt　nanofluids.　At　the　same　operating　conditions,　the　increases　in　the　latent　heat,　specific　heat,　and　thermal　conductivity　of　molten　salt　nanofluids　prepared　by　the　high-temperature　melting　method　were　1.2,　28.17,　and　35.71%　higher　than　those　by　the　aqueous　solution　method,　respectively.　SEM　observations　indicated　that　this　difference　in　thermal　performance　could　be　related　to　the　micromorphology.　In　the　aqueous　solution　method,　strong　natural　convection　during　water　evaporation　in　nanofluid　solution　induced　the　agglomeration　of　SiO2　NPs　and　hence　caused　uncertain　changes　in　micromorphology.　While　in　the　high-temperature　melting　method,　microcrystal　structures　around　NPs　kept　their　original　structures　during　the　cooling　process　due　to　the　close　density　of　SiO2　NPs　and　molten　salt.