Abstract: The oxidant-Fe₂O₃ composite adsorbents including H₂O₂-Fe₂O₃, NaClO-Fe₂O₃ and NaBr-Fe₂O₃ were prepared by chemical impregnation method. The oxidative adsorption of gas-phase As₂O₃ by Fe₂O₃ and the above three composite adsorbents was investigated through using the self-made arsenic generation and fixed bed adsorption reaction device. The total amount and valence of arsenic in the adsorbed products were detected nondestructively by high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry. The mechanism of catalytic oxidation of As（Ⅲ）/As（V） by Fe₂O₃ and NaBr-Fe₂O₃ adsorbents was deeply investigated. The results show that the adsorption capacity of NaBr-Fe₂O₃ is significantly enhanced, and it is about 2.3 times of that of Fe₂O₃. However, the adsorption properties of H₂O₂-Fe₂O₃ and NaClO-Fe₂O₃ are not improved. Both Fe₂O₃ and NaBr-Fe₂O₃ could oxidize As（Ⅲ） to As（V）, and the higher the Br- loading, the stronger the catalytic oxidation ability, and the stronger the adsorption capacity. The oxidative adsorption of gas-phase arsenic by Fe₂O₃ original sample follow the Mars-Maessen lattice oxygen oxidation mechanism. As（Ⅲ）oxidation could only be carried out in flue gas with the presence of oxygen. However, NaBr-Fe₂O₃ adsorbent could still oxidize As（Ⅲ） in the absence of O₂, the reason is that the strong electronegativity of Br- excites the activity of Fe-O bond of Fe₂O₃, which makes it easy to release active oxygen,thus improving the catalytic oxidation and adsorption activity,and Fe₂O₃ itself is reduced to Fe₃O₄.