Two series of catalysts, V2O5/TiO2 and modified V2O5/TiO2, were prepared with a conventional impregnation method. They were tested in the selective oxidation of toluene to benzoic acid under microwave irradiation. The reaction conditions were optimized over V2O5/TiO2 It was found that in the microwave catalytic process the optimum reactor bed temperature of the titled reaction decreases to 500 K (600 K in the conventional process). The modification of V2O5/TiO2 With MoO3, WO3, Nb2O5 or Ta2O5, which has no negative influence on the reaction in the conventional catalytic process, can greatly promote the catalytic activities in the microwave process, leading to a high yield of benzoic acid (similar to 41%). The effects of microwave electromagnetic held on the catalysts are discussed.