An ammonium salt of molybdenum heteropoly acid was loaded on silica support (HPA-SiO2), used as catalyst in oxidative desulfurization for removing benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) from model oil. The structural properties of prepared catalyst were studied by using various analytical techniques; Fourier transforms infrared spectroscopy , X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The results showed that the ammonium salt of molybdenum heteropoly acid highly dispersed on SiO2. The final catalyst exhibits good catalytic activity of oxidative desulfurization. The 94.6 % of thiophene compounds of the model oil were removed under optimal conditions; temperature at 80 °C, reaction time 100 min. The oxidation is decreased in order of DBT > 4,6-DMDBT > BT.