The sulfur in burning coal seriously affects the efficient utilization of coal. Introducting photocatalytic oxidation into the extraction desulfurization system can significantly improve the efficiency of ionic liquid reactive extraction desulfurization.In order to further study the mechanism of desulfurization, experiment and computer simulation were used to analyze it. The experimental results show that coupling the photocatalytic reaction process and the ionic liquid extraction process can effectively remove organic sulfur in coal. Among them [HO2MMim][HSO4]-H2O2-TiO2（10:10:4）photocatalytic treatment, the desulfurization rate of organic sulfur in the coal can reach 40.54%. Materials Studio analysis show that the hydroxyl radical (?OH) produced by photocatalysis has strong oxidizing properties, and the region near the oxygen atom of ?OH is electronegative, which is easy to form S=O double bond with the positively charged S atom in thiophene by electrostatic attraction. In addition, the addition of ionic liquid makes the original Lowest Unoccupied Molecular Orbital on the thiophene ring disappear, and also significantly reduces the energy level difference between HOMO orbital and LUMO orbital, making the reaction easier to proceed. Using COSMO software analysis, it is found that the ionic liquid extraction effect is show that the imidazole in [HO2MMim][HSO4] have a five-membered heterocyclic structure which formed bonds between thiophene and sulfone molecules through van der Waals force, so that the sulfides are continuously extracted into the ionic liquid phase. The addition of an oxidant makes the sulfone with the higher chemical potential more likely to enter the ionic liquid [HO2MMim][HSO4] with a lower chemical potential than thiophene.