12-Tungstophosphoric acid (PW) supported on KSF montmorillonite, PW/KSF, was used as catalyst for deep oxidative desulfurization (ODS) of mixed thiophenic compounds in model oil and crude oil under mild conditions using hydrogen peroxide (H₂O₂) as an oxidizing agent. A one-factor-at-a-time method was applied for optimizing the parameters such as temperature, reaction time, amount of catalyst, type of extractant and oxidant-tosulfur compounds (S-compounds) molar ratio. The corresponding products can be easily removed from the model oil by using ethanol as the best extractant. The results showed high catalytic activity of PW/KSF in the oxidative removal of dibenzothiophene (DBT) and mixed thiophenic model oil under atmospheric pressure at 75℃ in a biphasic system. To investigate the oxidation and adsorption effects of crude oil composition on ODS, the effects of cyclohexene, 1,7-octadiene and o-xylene with different concentrations were studied.