The lacunary Keggin 11-tungstophosphates were evaluated as catalysts for the oxidation of dibenzothiophene with hydrogen peroxide as oxidant in normal octane/acetonitrile biphasic system. The Na-5[PW11O(39)Ni] exhibited good catalytic activity with the desulfurization efficiency above 99.5%. The key factors affecting the reaction, including amount of catalyst, O/S molar ratio, catalyst dosage and initial sulfur content, were investigated, whereby the favorable conditions were determined. The presence and the oxidative effect of the peroxo-heteropoly species in the oxidative reaction were determined in the contrast experiments. Moreover, the Na-5[PW11O(39)Ni] catalyst was confirmed to have a high potential for deep desulfurization of diesel oil. [GRAPHICS] .