The double perovskite oxides Sr2Mg1-xMnxMoO6-delta (x=0, 0.2, 0.5, 0.8 and 1), formerly applied as anode materials for solid oxide fuel cells, were investigated as catalysts for the methane combustion. The mixed oxides were prepared by sol-gel procedures, followed by annealing under reducing atmosphere of 5% H-2 in nitrogen. The structure properties of these oxides were characterized in detail by X-ray diffraction, Xray photoelectron spectroscopy and X-ray absorption spectroscopy. The catalytic property was strongly influenced by the Mn substitution and the optimized activity was observed for Sr2Mg0.5Mn0.5MoO6-delta. The relation between catalytic performance and degree of Mn substitution was examined with regard to the structure and surface characteristics of the mixed oxides, which was discussed in view of the presence of oxygen vacancies and may be correlated with the Mn-relating surface lattice oxygen species. (C) 2010 Elsevier B.V. All rights reserved.