In　this　work,　we　investigated　the　methanol　steam　reforming　(MSR)　reaction　(CH3OH+H2O　-＞　CO2+3H(2))　catalyzed　by　alpha-MoC　by　means　of　density　functional　theory　calculations.　The　adsorption　behavior　of　the　relevant　intermediates　and　the　kinetics　of　the　elementary　steps　in　the　MSR　reaction　are　systematically　investigated.　The　results　show　that,　on　the　alpha-MoC(100)　surface,　the　O-H　bond　cleavage　of　CH3OH　leads　to　CH3O,　which　subsequently　dehydrogenate-,　to　CH2O.　Then,　the　formation　of　CH2OOH　between　CH2O　and　OH　is　favored　over　the　decomposition　to　CHO　and　H.　The　sequential　dehydrogenation　of　CH2OOH　results　in　a　high　selectivity　for　CO2.　In　contrast,　the　over-strong　adsorption　of　the　CH2O　intermediate　on　the　alpha-MoC(111)　surface　leads　to　its　dehydrogenation　to　CO　product.　In　addition,　we　found　that　OH　species,　which　is　produced　from　the　facile　water　activation,　help　the　O-H　bond　breaking　of　intermediates　by　lowering　the　reaction　energy　barrier.　This　work　not　only　reveals　the　catalytic　role　played　by　alpha-MoC(100)　in　the　MSR　reaction,　but　also　provides　theoretical　guidance　for　the　design　of　alpha-MoC-based　catalysts.