Molten　salts,　good　heat　transfer　and　thermal　storage　media,　show　potential　for　various　applications,　particularly　solar　thermal　power.　Nanofluid　technology　has　been　applied　to　molten　salts　to　improve　specific　heat.　In　this　study,　molten　salt　nanofluids　with　a　base　solution　of　binary　molten　salt　and　SiO2　nanoparticles　were　prepared　through　high-temperature　melting.　The　specific　heat　of　the　molten　salt　nanofluids　was　examined　with　different　diameters　and　mass　fractions　of　nanoparticles,　and　their　optimal　diameter　and　mass　fraction　were　determined.　The　thermophysical　properties　of　the　optimized　molten　salt　nanofluids　were　experimentally　tested　and　compared　with　those　of　pure　molten　salt.　Results　reveal　that　the　specific　heat　of　the　molten　salt　nanofluids　is　higher　than　that　of　the　pure　molten　salt.　The　optimal　mass　fraction　and　size　of　SiO2　nanoparticles　at　the　improved　specific　heat　of　the　molten　salt　nanofluids　are　1%　and　20　nm,　respectively.　The　optimal　specific　heat　of　the　molten　salt　nanofluids　is　17.8%　more　than　that　of　the　pure　molten　salt.　The　density　of　the　optimized　molten　salt　nanofluids　is　similar　to　that　of　the　pure　molten　salt,　and　the　average　thermal　conductivity　is　20.2%　more　than　that　of　the　pure　molten　salt.