Desulphurization of model and real oil samples was investigated using performic acid as oxidant assisted by air as co-oxidant. The catalysts used were Mo-oxide supported on ZSM-5 zeolite, which was synthesized in the laboratory and characterized by FT-IR, XRD, SEM and SSA analysis. In case of model oil, the optimum condition determined for complete oxidation of all the model compounds including thiophene, DBT and 4,6-DMDBT were; 60?C, 60 min, ambient pressure and air flow rate of 100 mL/min. The oxidation reactivity decreased from 4,6-DMDBT to DBT and thiophene, which was found to follow pseudo first order kinetics. The real oil sample used in the study included untreated naphtha (NP), light gas oil (LGO), heavy gas oil (HGO) and Athabasca bitumen (Bit.). In case of NP and LGO the sulfur removal of above 78% was attained whereas in case of HGO and Bit. samples about 60% of desulfurization was achieved.