A combined catalyst of quaternary ammonium bromide and phosphotungstic acid was used for dibenzothiophene (DBT) oxidation with hydrogen peroxide (H2O2) as the oxidant. The interaction between oxidized phosphotungstic acid and quaternary ammonium bromide was investigated in detail and the kinetic parameters were estimated. The oxidized phosphotungstic acid is extracted from the aqueous phase to the interface by quaternary ammonium bromide via a first-order extraction. The extraction capacity of different quaternary ammonium bromide is similar to each other. Kinetics study indicates that the rate constant decreases in the following order: octadecyltrimethylammonium bromide (STAB) > cetyltrimethylammonium bromide (CTAB) > (1-tetradecyl)trimethylammonium bromide (TTAB) > dodecyltrimethylammonium bromide (DTAB). An empirical equation was established for predicting reaction rate constant. Based on the kinetic study, the catalyst at the interface is observed to have greater effect on DBT oxidation, compared to that in the aqueous phase. The apparent activation energy (E-a) of 28.70 kJ/mol is obtained under the experimental conditions.