Vanadium – Magnesium mixed oxides used for the oxidative dehydrogenation were synthesized by impregnation method. Characterization of catalysts was determined by serial model techniques such as XRD and N2 physisorption. The result of XRD showed that V2O5 phase was inhibited in the V-Mg-O mixed oxides prepared with impregnation method. Catalyst test performance showed high selectivity for the oxidative dehydrogenation of n-butane to butene and butadiene.