Single phase specimen of polycrystalline Ba2Fe2O5, which has been a candidate for CO2 absorbents, was prepared by solid state reaction method in N-2 gas flow (log p(O-2) similar to 10(-4) atm). Ba2Fe2O5 showed weight increase above 500 degrees C in CO2 gas flow, which is originated from the CO2 absorption. In CO2 gas flow, the weight decrease due to the CO2 desorption was observed above 1100 degrees C. Thermogravimetry and X-ray diffraction measurements have revealed that Ba2Fe2O5 can reversibly react with CO2, which is represented as Ba2Fe2O5 + CO2 <-> BaCO3 + BaFe2O4. Thermodynamic calculation of the reaction was carried out, showing agreement with the results obtained by thermogravimetry. From the calculation, it has been revealed that Ba2Fe2O5 can react with CO2 at a higher temperature than Li4SiO4 regardless of partial pressure of CO2 (p(CO2)), indicating that Ba2Fe2O5 has a higher potential as CO2 absorbent than Li4SiO4.