Molten　salt,　with　wide　using　temperature　range,　low　vapor　pressure,　large　heat　capacity,　low　viscosity,　good　thermal　stability,　low　cost　and　so　on,　has　become　recognized　as　a　considerable　regenerative　potential　of　the　heat　transfer　medium　for　solar　thermal　power　generation.　Accurate　thermal　property　data　of　molten　salt　has　a　major　impact　on　heat　transfer　and　storage　performance　of　medium　used　in　solar　thermal　power　generation.　Viscosity　of　molten　salt,　as　an　important　one　of　thermal　properties,　has　a　decisive　role　on　improving　heat　transfer　efficiency　and　reducing　flow　resistance.　In　this　paper,　viscosity-temperature　characteristics　of　water　and　HITEC　were　measured　by　using　developed　high-temperature　viscometer,　and　the　results　were　agreement　with　literature　data　to　prove　the　reliability　of　this　high-temperature　molten　salt　viscometer.　In　order　to　reduce　the　melting　point　of　mixed　molten　salt　and　improve　their　thermal　properties,　based　on　Solar　Salt,　two　new　kinds　of　molten　salts　with　low　melting　point　were　obtained　through　modification,　whose　viscosity-temperature　characteristics　were　studied　further.　The　results　show　that　viscosity　of　modified　high-temperature　molten　salt　decreased　at　a　certain　degree,　that　is　helpful　to　reduce　the　resistance　of　molten　salt　heat　transfer　system　and　cost　of　solar　thermal　power　generation.