Nine　kinds　of　binary　nitrate　salts　with　different　ratio　of　KNO3　and　NaNO3　were　prepared　and　the　DSC　(Differential　Scanning　Calorimetry)　curves　were　obtained　by　using　STA409-PC　manufactured　by　Netschi　company　from　Germany.　The　measured　results　showed　that　the　binary　nitrate　salts　with　the　ratio　of　KNO3　and　NaNO3　in　4:6,　6:4,　5:5　and　9:1　have　eutectic　and　others　have　no　eutectic.　Then　two　prepared　methods　were　used　to　prepare　the　binary　nitrate　salts.　The　DSC　curves　and　TG　curves　of　prepared　molten　salts　were　obtained　and　analyzed.　The　results　showed　that　these　two　methods　are　both　valid　in　making　up　eutectic　mixed　nitrate.　The　melting　points　of　the　binary　nitrate　salts　prepared　by　the　two　methods　are　very　close,　In　addition,　there　is　no　big　change　about　its　melting　point　and　decomposition　point　after　nitrate　molten　salts　are　heated　repeatly.　A　simple　method　of　binary　nitrate　salts　preparation　at　large　scale　was　proved　to　be　valid　by　the　experiments.