Abstract: Nanofluid composed of molten salt and nanoparticles are important materials for the effective power ge-neration and heat storage system of solar energy.It is of great significance to find out why nanoparticles are able to enhance the specific heat capacity of molten salt.In this paper，nanoparticles were added in molten salt at diffe-rent contents，and the specific heat capacity variation of complex fluids was measured by means of DSC.Then，the molecular dynamic simulation was adopted to explore the reason for the rise of specific heat capacity of complex fluids.In the simulation，the number of molten salt molecules is fixed and the content of nanoparticles is changeable，so as to analyze the effects of the content of nanoparticles on the specific heat capacity，structure and distribution of molten salt.It is indicated that，when the mass fraction of nanoparticles is 1.0%~1.5%，the increase of specific heat capacity is the largest.The additional interaction force produced by the high-density clustering of molten salt anions on the surface of nanoparticles or by the regular restricted distribution on the surface of nanoparticles with smaller particle size （about 1nm） is the main reason for the increase of the specific heat capacity of nano-fluids.In addition，calculation results confirm the positive correlation between the dispersity of the nanoparticles and the increase of specific heat capacity.The addition of nanoparticles can reduce the distance between anion and cation in molten salt to a certain extent，resulting in the change of Coulomb energy，which is another reason for the increase of specific heat capacity.

Key words: heat transfer and storage material, molten salt, nanofluid, molecular simulation, specific heat capacity, microstructure