Benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethlydibenzothiophene (4,6-DMDBT) were extracted from an oil phase to ionic liquid phase, and then oxidized to the corresponding sulfone by the cheap catalyst, N-hydroxyphthalimide (NHPI), using molecular oxygen as the oxidant in one-pot. The system can be recycled 5 times without a significant decrease in desulfurization.