The utility model provides a fused salt-based nanofluid preparation system which comprises a high-temperature pool and a low-temperature pool which are communicated with each other, and fluid flows unidirectionally between the high-temperature pool and the low-temperature pool through a first passage. In the high-temperature pool, the fused salt-based solution and the nanoparticles are added fromthe fused salt inlet and the nanoparticle inlet respectively, so that the nanoparticles in the prepared nanofluid can be kept at proper density, and the nanofluid can achieve expected thermodynamic properties. And in the low-temperature pool, the temperature in the low-temperature pool is higher than the melting point of the nanofluid and lower than the temperature in the high-temperature pool, and the low-temperature pool is used for storing the nanofluid and enabling the nanofluid to be at a temperature capable of enabling the nanoparticles in the nanofluid to be uniformly distributed. The low-temperature pool is connected with the application terminal through the second passage, and the nanofluid is supplied to the application terminal through the second passage.