The invention discloses a low-melting-point nano molten salt heat transfer and storage medium and a preparation method and belongs to the technical field of physical heat transfer and energy storage in advanced technologies. The low-melting-point nano molten salt heat transfer and storage medium is prepared from low-melting-point mixed molten salt and nanoparticles in a composite mode. The low-melting-point mixed molten salt is mainly composed of potassium nitrate, sodium nitrate, calcium nitrate and lithium nitrate. The nanoparticles are nanoparticles of metallic oxide or nonmetallic oxide. According to the novel low-melting-point nano molten salt prepared through the method, the melting point is 80-130 DEG C, the decomposition temperature is approximately 600 DEG C, and compared with the low-melting-point mixed molten salt, the using temperature range of the low-melting-point nano molten salt does not change greatly, but the specific heat is improved remarkably by about 10-60%.