<p>Thermal storage is a key technology in concentrating solar thermal power (CSP) system, which can provide continuous and stable high quality electricity, improve the efficiency of the power system and extend the system life. Molten salt is an important material for heat storage and heat transfer in solar thermal power generation, the addition of nanoparticles can synergistically and effectively enhance both specific heat capacity and thermal conductivity. In this study, a base salt with mass percentage of 31.5% Na₂CO₃-31.5% Li₂CO₃-37% K₂CO₃ was employed. SiO₂ nanoparticles with varying particle sizes, different concentrations of SiO₂ and Al₂O₃, as well as composite nanoparticles, were dispersed in a salt solution to create ternary carbonate nanofluids using a two-step solution method. The melting point, specific heat capacity, crystal structure, and surface microstructure of nanofluids were measured using a differential scanning calorimeter, X-ray diffractometer and scanning electron microscope, respectively. The results show that among the selected nanoparticles, SiO₂ nanoparticles are the most effective at enhancing the specific heat capacity and thermal conductivity of the ternary carbonates. The mass addition of 1.0% of 30 nm SiO₂ results in 83.5% increase in specific heat capacity in the solid phase and 159.4% increase in the liquid phase compared to pure ternary carbonates, and the thermal conductivity increases by 20.8%. Meanwhile, scanning electron microscopy has revealed the formation of rod-like nanostructures after adding nanoparticles to ternary carbonates. XRD results confirm that there are no chemical reactions between ternary carbonates and the added nanoparticles. After exposure to a constant high temperature of 600°C for 100 h and undergoing 100 cycles of large temperature differences (ranging from room temperature to 600°C), the thermophysical properties of this composite material remain relatively stable, demonstrating good long-term and heating-cooling cycle thermal stability.</p>