Abstract: In this paper, the adsorption performance of NaHCO₃ on SeO₂ at 140−220 ℃ is investigated by adsorption experiments, and the total amount, valence and morphology of selenium in the adsorbed samples are resolved by series characterization, and the adsorption mechanism of NaHCO₃ on SeO₂ is discussed in depth by combining with density functional theory calculations. The results show that the adsorption performance of NaHCO₃ on SeO₂ increases with the increase of temperature, and the thermal decomposition reaction of NaHCO₃ to Na₂CO₃ occurs simultaneously during the adsorption process, and the Na₂CO₃ produced after the thermal decomposition has stronger adsorption activity. The SeO₂ adsorption process belongs to the chemical adsorption of Se atoms in SeO₂ bonded to O atoms on the surface of Na₂CO₃, and the adsorption products are mainly selenite.