Methane　(CH4)　oxidation　is　an　important　reaction　to　reduce　the　greenhouse　effect　caused　by　incomplete　combustion　of　CH4.　Here,　we　explored　the　mechanism　of　CH4　oxidation　catalyzed　by　CeO2　and　Ni-doped　CeO2,　focusing　on　the　redox　properties　of　these　catalyst　surfaces,　using　density　functional　theory　(DFT).　We　found　that　the　barriers　for　CH4*　activation　and　H2O*　formation　are　correlated　with　the　surface　redox　capacity,　which　is　enhanced　by　Ni　doping.　Furthermore,　the　complete　reaction　mechanism　is　explored　by　DFT　calculations　and　microkinetic　simulations　on　bare　and　Ni-doped　CeO2　surfaces.　Our　calculations　suggest　that　the　doping　of　Ni　leads　to　a　much　higher　overall　reactivity,　due　to　a　balance　between　the　CH4*activation　and　H2O*　formation　steps.　These　results　provide　insights　into　the　CH4　oxidation　mechanism　and　the　intrinsic　relationship　between　redox　properties　and　the　activity　of　CeO2　surfaces.