Desulfurization of diesel oil using oxidative extraction method with ionic liquids n-butyl methylimidazolium hydrosulfate ([BMIM][HSO4]) and n-butyl pyridine hydrosulfate ([BPy][HSO4]) was conducted. When using H2O2/HCOOH oxidative system, the sulfur compounds transfer to more polar compounds (corresponding sulfones and sulfoxides), which are more easily dissolved in ionic liquids. The distribution coefficients of sulfur compounds in ionic liquids increase, therefore, the extraction yield raises. Ionic liquids can be regenerated by reextraction of sulfur compounds using some low boiling point solvents (cyc1ohexane and etyl acetate). Those solvents can be recovered by simple distillation and reused.