In this paper, density functional theory (DFT) method is used to study the adsorption behavior of As₂O₃ on α-Fe₂O₃(001) surface and the influence of doping Mo, Mn and Ni on the adsorption behavior of As₂O₃ on α-Fe₂O₃(001) surface. The adsorption model of As₂O₃ on the surface of α-Fe₂O₃(001) and the adsorption model of Mo, Mn and Ni doping were established. The adsorption energy of As₂O₃ on the catalyst surface was calculated. The density of bonding states and the charge layout of As₂O₃ on the surface of α-Fe₂O₃(001) before and after doping are analyzed. Electron transfer occurs in the four systems. Mo doping activates As₂O₃ molecules, makes As₂O₃ tend to be adsorbed on Mo active sites, protects Fe active sites, and enhances the anti-arsenic poisoning ability of α-Fe₂O₃. After Mn and Ni doping, the reaction activity of As₂O₃ is lower than before, which inhibits the adsorption of As₂O₃ and increases the poisoning effect of the catalyst, which is not conducive to the subsequent NH₃-SCR reaction.