Abstract: The development of highly active functionalized ionic liquids (ILs) as both extractants and catalysts for use in achieving deep desulfurization continues to pose challenges. In this study, a highly efficient oxidative desulfurization system was constructed, composed of dual-acidic ionic liquids (DILs) and H2O2-AcOH. The investigation results of four DILs prepared from different metal chlorides ([HSO3C3NEt3]Cl-MnCln, MnCln = AlCl3, ZnCl2, CuCl2, FeCl3) in oxidative desulfurization showed that [HSO3C3NEt3]Cl-AlCl3 had an outstanding catalytic effect and significantly promoted the oxidation of sulfides. With a 0.2 g [HSO3C3NEt3]Cl-AlCl3, the removal rate of dibenzothiophene (DBT) reached 100% in 10 mL model oil under mild conditions at 55 °C for 20 min. The key is its ability to induce the dismutation of superoxide anions (•O2−), which facilitates the generation of singlet oxygen (1O2). The efficient oxidation of DBT is accomplished through a predominantly 1O2-mediated non-radical mechanism. [HSO3C3NEt3]Cl-AlCl3 serves as a favorable medium for contact to be made between 1O2 and sulfides, which indicates an efficient catalytic-adsorption synergy.