Abstract: After desulphurization, the trace amount of SO₂ in the tail gas of coal-fired power plant will lead to the deterioration of CO₂ adsorption performance of potassium-based adsorbent. Using crystalline aluminum chloride as precursor, the solid adsorbent K₂CO₃/Al₂O₃ was prepared by sol-gel method. The adsorption characteristics of CO₂ in SO₂ (0, 150, 250 and 400 mg/m³) atmosphere were simulated by fixed bed reaction system. Combined with the BET and XRD characterization methods, the pore structure and material composition of the adsorbent were analyzed. The influence of SO₂ on the surface adsorption of CO₂ by K₂CO₃/Al₂O₃(0001) was studied by using the DFT theory. The results showed that in the ideal atmosphere, the cumulative adsorption capacity of CO₂ of potassium adsorbent is 1.72 mmol/g. In the presence of 150 mg/m³ SO₂ in the reaction atmosphere, the potassium adsorbent reacts with SO₂ to form K₂SO₃, resulting in a 19.77% decrease in adsorption capacity (1.38 mmol/g). When the concentration of SO₂ increases to 400 mg/m³, the cumulative adsorption capacity of CO₂ of potassium-based adsorbent gradually decreases to 1.26 mmol/g, the adsorption performance of CO₂ of the adsorbent is deteriorated. The adsorption capacity of potassium-based adsorbent decreases to 1.1 mmol/g after seven cycles, and the cycle performance is deteriorated. The adsorption sites of CO₂ and SO₂ on the surface of K₂CO₃/Al₂O₃(0001) are Al-O bridge sites, and the H₂O molecules are O top sites. The adsorption of SO₂ on K₂CO₃/Al₂O₃(0001) surface is greater than that on H₂O and CO₂. When H₂O and CO₂ are co-adsorbed, the O-s orbitals and H-s orbitals overlap in the CO₂ molecules, so that the two can promote each other during surface adsorption. Due to the active p orbitals of S and O atoms, the SO₂ molecules preferentially preempt the adsorption site of CO₂ and inhibit the adsorption of CO₂ on the surface when co-adsorbed with CO₂. The catalytic effect of H₂O molecules on the adsorption of SO₂ on the surface of K₂CO₃/Al₂O₃(0001) is greater than that of CO₂. The presence of H₂O will accelerate the reaction between SO₂ and the surface, leading to the deterioration of the adsorption capacity of CO₂ on the surface of the adsorbent. When CO₂ and H₂O are co-adsorbed on K₂CO₃/Al₂O₃(0001) surface, the carbonation mechanism is H⁺ and OH⁻ in H₂O molecules, which forms \mathrmHCO_3^- with \mathrmCO_3^2- and CO₂ respectively. The reaction energy barrier is 1.12 eV, and the reaction heat is −1.47 eV.