The electronic properties of the pristine and alkali metals doped CaO(100) surfaces, as well as their propensity toward CO2 and SO2sorption are studied using the dispersion-corrected density functional theory (DFT-D). Various interaction modes between the acidic gas and surfaces are considered. The results show that the basic oxygen surface sites are active adsorption sites for CO2 and SO2, with monodentate-like coordination formed on each surface. Further, charge analysis is conducted, showing a charge transfer fromeach surface to the adsorbate. The comparison of adsorption energies indicates that CO2 and SO2 show stronger adsorption on alkali metal-doped CaO than that on pristine CaO. The metal Csis the preferred dopant for high sorption capacity, whichhave agreat strengthening effect onCO2 and SO2 binding.