The catalytic performances of Mo-V-Sb mixed oxide catalysts have been studied in the selective oxidation of isobutane into methacrolein. V-Sb mixed oxide showed the activity for oxidative dehydrogenation of isobutane to isobutene. The selectivity to methacrolein increased by the addition of molybdenum species to the V-Sb mixed oxide catalyst. In a series of Mo-V-Sb oxide catalysts, Mo1V1Sb10Ox exhibited the highest selectivity to methacrolein at 440 degrees C. The structure analyses by XRD, laser Raman spectroscopy and XPS showed the coexistence of highly dispersed molybdenum suboxide, VSbO4 and alpha-Sb2O4 phases in the Mo1V1Sb10Ox. The high catalytic activity of Mo1V1Sb10Ox can be explained by the bifunctional mechanism of highly dispersed molybdenum suboxide and VSbO4 phases. It is likely that the oxidative dehydrogenation of isobutane proceeds on the VSbO4 phase followed by the oxidation of isobutene into methacrolein on the molybdenum suboxide phase.