High-purity rare-earth orthovanadates (R _E VO ₄ ), PrVO ₄ , GdVO ₄ , DyVO ₄ , HoVO ₄ , ErVO ₄ , NdVO ₄ , TbVO ₄ and LuVO ₄ , have been prepared by the citrate method. XRD, FTIR, LRS, UV–VIS diffuse reflectance, TPR and EPR techniques have been employed to characterize them. The catalytic performances of PrVO ₄ , ErVO ₄ , GdVO ₄ , DyVO ₄ and NdVO ₄ in the oxidative dehydrogenation of propane can compete with that of Mg ₃ V ₂ O ₈ . The selectivity of propene over TbVO ₄ , LuVO ₄ and HoVO ₄ was relatively low. TPR results showed that the more easily the catalyst is reduced, the higher the propene selectivity. EPR and in situ Raman experiments confirmed the presence of low-valence vanadates at the catalyst surface in the reaction process. We observed that ¹⁸ O ₂ -isotope exchange occurred over the catalysts via a double-step single exchange process and the activity of the catalysts increased with an increase of isotope exchange rate.