Functionalized ionic liquids (ILs) have been considered as efficient catalysts for oxidative desulfurization (ODS), but the further industrial applications are hampered by the poor separability with oil phase after reaction and large dosage. In this work, few-layered graphitic carbon nitride (g-C3N4) with high specific surface area was prepared via thermal oxidation and employed as a carrier to construct supported ionic liquid catalyst for ODS. A functional quaternary phosphonium ionic liquid [(C6H13)(3)PC14H29](3)PMo12O40 (abbreviated as C14PPMo) was synthesized and immobilized on g-C3N4. Then, the as-prepared samples were characterized by FT-IR, DRS, XRD, N-2 adsorption-desorption isotherm, XPS, SEM, and TEM, systematically. It was found that few layer g-C3N4 had a large specific surface area (194.89 m(2) g(-1)), which was conducive to the high dispersion of C14PPMo IL. The obtained support catalyst C14PPMo/g-C3N4 exhibited outstanding catalytic ability on the oxidation of dibenzothiophene (DBT), and the desulfurization efficiency could reach 100% with a small dosage of IL under optimal conditions. The oxidative products of DBT and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were the homologous sulfones and proved by GC-MS, and the proposed reaction processes were studied, respectively. Since the supported IL was a heterogeneous catalyst and no additional solvent was added, C14PPMo IL could be separated and repossessed readily after the reaction. Moreover, the recycle ability of C14PPMo/g-C3N4 on the oxidation of both DBT and 4,6-DMDBT were investigated simultaneously, and both of the desulfurization activities could still remain above 90% after 6 times cycling.