In this paper, first, activated carbon (AC) with high specific surface area was modified with metal ionsFe³⁺,Cu²⁺ and Ag⁺ through an impregnation process, and three kinds of modified AC, namely, Fe³⁺ / AC, Cu²⁺ / ACand Ag⁺ / AC, were prepared. Next, the products were used to adsorb the dibenzothiophene (DBT) in acetonitrilesolution, and the corresponding isotherms were obtained by means of the static adsorption method. Then, the de-sorption peak areas of DBT desorbed from the AC before and after the modification were measured through tempera-ture-programmed desorption (TPD) experiments. Finally, the total amount of acidic functional groups on the sur-faces of these four kinds of AC was measured via the Boehm titration. The results show that, after the modification,both the total amount of acidic functional groups and the adsorption capacity for DBT increase, that the total amountof acidic functional groups follows the order of Fe³⁺ / AC>Cu²⁺ / AC>Ag⁺ / AC>AC, with the adsorption capacity re-spectively increasing by 30%, 20% and 14%. It is thus concluded that the adsorption capacity of AC absorbents isproportional to the total amount of acidic functional groups, and that the loading of Fe³⁺,Cu²⁺ and Ag⁺ on AC en-hances the adsorption of DBT in acetonitrile solution due to the increase of active sites on AC surfaces for DBT ad-sorption.