The ultrasound-assisted oxidative desulfurization (UAOD) process has been applied to a number of diesel fuels containing varying amounts of sulfur content. The transition metal complex and quaternary ammonium salts (QAS) phase transfer agents have been applied with aqueous hydrogen peroxide as oxidizing agent. High yield of 3-bromobenzothiophene, and 2-bromobenzothiphene sulfone has been found from phase transfer agents containing tetraoctylammonium bromide. No contaminates such as bromo compound derivates had been isolated when the new fluoride phase transfer agent was used. Selectivity was particularly high for this process as demonstrated by selective ions mass spectrometry. The experiment also demonstrated that the catalyst could be recovered for reuse. Furthermore, the hydrogen peroxide provides a good performance, and the oxidation will proceed as low as 0.25%.