Abstract: The thermodynamic and economic performance models of solar power tower system based on supercritical CO₂ Brayton cycle are established. The average annual efficiencies of the systems under different installed capacity are compared. The cost proportion of each item and its variation with the increase of installed capacity are analyzed. The methods to further reduce the cost of power generation are proposed. The results show that the average annual efficiency of the system first increases and then decreases with the increase of installed capacity,and its peak value is 17.4% at 20 MW,which is mainly affected by the solar field efficiency. The levelized cost of energy decreases with the increase of installed capacity,from 0.477 /kWh at 1 MW to 0.125 /kWh at 100 MW.Reducing the investment costs of solar field and thermal energy storage are the keys to reduce the power generation cost of large-scale power plant.