Molten　salt　is　popularly　used　as　high　temperature　heat　transfer　and　thermal　energy　storage　medium.　In　order　to　decrease　the　melting　point　and　increase　decomposition　temperature　of　molten　salt,　phase　diagrams　for　KNO3-　3-　NaNO2　2　binary　nitrates　were　calculated.　And　the　binary　salt　with　the　lowest　eutectic　point　was　prepared.　Furthermore,　the　effect　of　Na2CO3　2　CO　3　addition　on　optimal　selected　KNO3-NaNO2　3-NaNO　2　binary　molten　salt　thermophysical　properties　and　corrosion　behavior　are　experimentally　investigated.　The　results　show　that　the　addition　of　7　wt%　Na2CO3　2　CO　3　to　KNO3-NaNO2　3-NaNO　2　binary　molten　salt　can　lower　the　melting　point　by　5.8　%.　The　addition　of　9　wt%　Na2CO3　2　CO　3　to　KNO3-NaNO2　3-NaNO　2　binary　molten　salt　can　increase　the　decomposition　temperature　by　20.6　%,　enhance　the　specific　heat　capacity　by　4.8　%　and　increase　the　thermal　conductivity　by　7.5　%,　but　at　the　same　time　viscosity　increased　about　70　%　at　300　degrees　C.　Meanwhile,　the　density　increases　with　the　increase　of　Na2CO3　2　CO　3　content　addition.　The　average　corrosion　rate　of　316　stainless　steel　increases　with　the　increasing　of　Na2CO3　2　CO　3　content,　which　is　consistent　with　the　cross-section　SEM　results.