The desulfurization of untreated petroleum oil is required in order to comply with stringent environmental regulations. Ultrasound-assisted oxidative desulfurization (UAOD) is an innovative technology for sulfur removal in order to avoid the environmental hazards associated with the combustion of sulfur compounds in raw diesel oil. In this study, diesel oil is treated through UAOD. The effects of ultrasound time (6-30 min), amplitude (20-60%), phase transfer agent (100-500mg), catalyst dosage (10-500mg), H2O2 concentration (30-50%v/v), organic to aqueous phase (OP:AP) ratio (50:50-90:10) and reaction temperature (30-70℃) were examined. The screening analysis used is the definitive screening design that statistically determines the parameters that have a significant effect on the oxidation of diesel oil. Results indicate that significant factors (p-value < 0.5) where ultrasound time, amplitude, catalyst dosage and reaction temperature; while the phase transfer agent, H2O2 concentration and OP:AP ratio were insignificant (p-value > 0.5) on the response of sulfur conversion in the untreated diesel oil. This study concludes that the essential factors to achieve deep desulfurization in diesel oil include ultrasound time, amplitude, H2O2 concentration and reaction temperature which are key factors in the oxidation of sulfur compounds to achieve low sulfur containing diesel oil.