The presence of sulphur in heavy crude oil posed enormous challenges as regards its negative environmental and economic impacts. In this study, the oxidation-extraction desulphurization of heavy crude oil was conducted with Fenton's reagent, KMnO4, and KMnO4+H2O2 as oxidants over acetic and formic acid catalyst at different oxidant/catalyst oxidation system, at temperature of 60 and 80 C respectively and pressure in the reaction was atmospheric. After the oxidation reaction, the oxidized oil was extracted with DMSO for separation of sulphoxide. The desulphurized oil was analysed using XRF sulphur-in-oil analyser and FT-IR spectrophotometric analysis. The highest desulphurization was obtained at the oxidation temperature of 60 C for 15 minutes with a KMnO4+H2O2/HCOOH oxidant/catalyst oxidation system, the desulphurization of 73.00% was achieved. The different oxidation reaction tests showed that, increasing reaction temperature slightly increased the desulphurization. KMnO4/H2O2 combination was better than Fe2+/H2O2 (Fenton's reagent) as organic sulphur oxidant in the presence of HCOOH as catalyst. However DMSO was found to be a poor solvent for extraction of oxidized sulphur.