Molten　salts　are　widely　applied　as　heat　transfer　and　thermal　storage　medium　for　solar　thermal　power.　In　order　to　research　the　effect　of　preparation　conditions　and　the　types　of　nanoparticles　on　the　thermophysical　properties　of　molten　salt　nanocomposite,　different　molten　salt　nanocomposites　were　developed　by　mixing　the　nitrates　(Ca　(NO3)2·4H2O–KNO3–NaNO3–NaNO2)　with　1.0　wt%　of　SiO2,　MgO,　TiO2　and　CuO　nanoparticles　using　a　microwave　method,　which　was　a　new　preparation　process　of　molten　salt　nanocomposite　based　on　high　temperature　mixing　without　water.　The　effect　of　different　microwave　heating　temperature　(250,　350　and　450　°C)　and　heating　time　(30,　60,　90　and　120　min)　were　experimentally　studied.　The　melting　point,　latent　heat　and　specific　heat　of　the　samples　were　analyzed　by　differential　scanning　calorimeter　(DSC).　The　morphology　was　observed　by　scanning　electron　microscope　(SEM).　The　results　showed　that　the　nanoparticles　induced　a　decrease　of　the　melting　point　of　0.1–2.4%　while　the　latent　heat　decreased　by　3.3–7.9%.　Compared　with　other　molten　salt　nanocomposites,　the　molten　salt　with　the　addition　of　SiO2　nanoparticles　had　the　biggest　increase　in　specific　heat,　which　increased　by　7.7%　in　solid　state　and　21.0%　in　liquid　state　after　heating　for　90　min　at　250　°C.　The　total　heat　storage　density　could　reach　to　783.0　J/g　between　30　and　500　°C,　which　was　13.3%　higher　than　the　base　salt.　In　addition,　according　to　the　morphology　of　the　samples,　network　nanostructures　were　observed　in　the　molten　salt　nanocomposite　doped　with　SiO2.　©　2020　Elsevier　B.V.