By leveraging its catalytic oxidation effect to remove dibenzothiophene (DBT) from model oil, a novel di-[EtPy]/[CoCl3] ionic liquid catalyzer was created using 1,4-dichlorobutane, pyridine, and cobalt chloride. The product was characterized by nuclear magnetic resonance (HNMR), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), and scanning electron microscopy (SEM-Mapping-EDS). This study constructed an extraction catalytic oxidation system (ECODS) using di-[EtPy]/[CoCl3] catalyst, ketone oxide (PMS) as oxidant, and acetonitrile as extractant to explore the catalytic activity and the removal effect of DBT in octane. The double-end structure of the double ionic liquid gave the catalyst a twofold chance of making contact with the oxidant once it was added, enhancing the release of the sulfate radical from the catalytic oxidant. Under the optimal desulfurization conditions: m(oil)=6 g, m(di-[EtPy]/[CoCl3])=0.10 g, m(acetonitrile)=1.00 g, m[PMS (20wt%)]=0.50 g, t=70 min, T=45.0℃, the removal rate of DBT in fuel oil could be as high as 96.86%. The analysis showed that the dipyridine ring of the catalyst strengthens the π bond and electrostatic interaction with DBT, and the double catalytic sites were the main reasons for the high catalytic efficiency. The desulfurization rate of di-[EtPy]/[CoCl3] catalyst after five cycles was more than 86.00%, which was mainly due to the interaction of ionic liquid and metal ions reducing the loss of catalyst. Finally, the oxidation product was identified as dibenzothiophene sulfone (DBTO2) by GC-MS, and the mechanism of the oxidation process was preliminarily discussed. The research showed that the di-[EtPy]/[CoCl3] ionic liquid as a catalyst had high catalytic activity and desulfurization performance, providing a new catalyst and process system for the industrial removal of DBT.