A series of Sn-Cr composite oxide catalysts with various Sn/Cr mote ratios were prepared and used for CH4 deep oxidation. Compared with pure SnO2 and Cr2O3, the activity and thermal stability of Sn-Cr binary catalysts were significantly enhanced. The optimal activity was achieved on those samples with Sn/Cr mole ratios around 50:50. XRD results demonstrated that Cr3+ was doped into the crystal lattice of rutile structure SnO2 to form solid solution. As a result, the crystallization of the Sn-Cr samples was retarded, thus higher surface areas and lower crystallinity of them were maintained. TPR and XPS substantiated that more active oxygen species was formed in the Sn-Cr binary catalysts. Indeed, the high surface areas of the Sn-Cr composite oxides and the presence of more active oxygen species in them are considered as the two main reasons leading to their enhanced CH4 oxidation activity.