MoV0.3Te0.17 and MoV0.3Te0.17Nb0.12 catalysts were prepared by a hydrothermal synthesis route and tested for the oxidation of isobutane and isobutene. Characterization results showed that the structure and property of Mo-V-Te-based catalysts are relatively different depending on the presence of the Nb element. Catalytic tests showed that the selectivity of methacrolein can comparatively be improved by the addition of Nb into the MoV0.3Te0.17 catalyst for the selective oxidation of isobutane.