Abstract: H₂O₂ was used to modify activated carbon in order to investigate the effect of oxygen-containing functional groups on the ability of activated carbon to convert NO₂ to NO. The catalysts before and after modification were characterized by N₂ physical adsorption desorption, Boehm titration, X-ray photoelectron spectroscopy, Raman spectroscopy, and their ability to convert NO₂ was evaluated. The result shows that hydrogen peroxide surface modification increases microporous areas of activated carbon and contents of surface oxygen-containing functional groups especially surface phenolic hydroxyl groups, thereby promoting the adsorption and catalytic conversion of NO₂ on activated carbon surface. The reaction performance of AC-2 was the best and its NO₂ conversion rate was 99.8% at 150 ℃.