Particle size dependence of CO2 absorption rate of powdered Ba2Fe2O5 with three kinds of particle size was studied by XRD, SEM, particle size distribution measurement and thermogravimetry. From the particle size distribution measurement, average particle sizes of the powdered Ba2Fe2O5 samples were estimated about 52.5 mu m, 77.5 mu m and 100.0 mu m, respectively. Results show that the reaction of CO2 with Ba2Fe2O5 was controlled by the diffusion step in the product layer, and the kinetics process could be described by the RPP model (Real Physical Picture). Moreover, Ba2Fe2O5 exhibits a good recycling performance though the adsorption capacity is reduced slightly during the cycle processes, and the pathway of the CO2 adsorption-desorption on Ba2Fe2O5 has also been obtained, which suggested that Ba2Fe2O5 is a promising CO2 absorbent material.