Abstract: Based on the FLUENT software, heat storage process of 8 h and heat release process of 16 h for the integrated receiver-storage units were numerically simulated, the temperature distribution of rock and air in the packed bed was obtained, its heat transfer characteristics were studied, and the influencing factors of thermal performance were analyzed. The results show that during the heat storage process, the axial and radial temperature distribution of the packed bed are not uniform. Thermo-cline appears along the axial direction, and a local high temperature area appears along the radial direction on the upper part of the packed bed. The axial and radial temperature distribution over time is influenced by the existence of the return pipe. At the equilibrium point, the rock temperature equals to the air temperature. The efficiency for 8 h heat storage process of the integrated receiver-storage unit is 97.6%.The position in height of the return pipe outlet from the ground does not affect the thermal efficiency. The pressure difference of the circulating fan mainly affects the heat release efficiency and solar-to-heat efficiency. The average diameter of the rock particles mainly affects the absorption efficiency and heat release efficiency.