In order to improve the catalytic activity of magnesium ortho-vanadate (Mg3V2O8.) for the oxidative dehydrogenation of propane, Mg3V2O8, doped with Fe3+, (Fe-Mg3V2O8) was prepared. The improvement of the conversion of propane from 4.8% on Mg3V2O8 to 8.2% on 5% Fe-Mg3V2O8 together with the rather similar selectivity to propylene on un-doped and doped catalysts (62.3 and 61.0%, respectively). To evaluate the redox nature of Fe-Mg3V2O8 during the oxidative dehydrogenation, the catalysts used for the conversion of propane with and without gaseous oxygen were analyzed by XRD, solid state V-51 MAS NMR, XAFS, and XPS. After the propane conversion without oxygen, complete conversion of Fe-Mg3V2O8 to Mg2VO4 and MgO together with a small amount of Fe2O3 was observed by XRD, while the reduction of V5+ to V4+ was detected by V-51 MAS NMR and V K-edge XAFS from the catalyst. However XPS analysis showed that such a reduction was not observed over the surface of Fe-Mg3V2O8, since oxygen was supplied from bulk to the surface of the catalyst to keep V5+ over the surface. After the treatment of the reduced catalysts with gaseous oxygen, the complete regeneration of Fe-Mg3V2O8 from the reduced phase was confirmed by those analyses.