The　catalytic　mechanisms　of　nitrogen　reduction　reaction　(NRR)　on　the　pristine　and　Co/alpha-MoC(001)　surfaces　were　explored　by　density　functional　theory　calculations.　The　results　show　that　the　preferred　pathway　is　that　a　direct　N　equivalent　to　N　cleavage　occurs　first,　followed　by　continuous　hydrogenations.　The　production　of　second　NH3　molecule　is　identified　as　the　rate-limiting　step　on　both　systems　with　kinetic　barriers　of　1.5　and　2.0　eV,　respectively,　indicating　that　N-2-to-NH3　transformation　on　bimetallic　surface　is　more　likely　to　occur.　The　two　components　of　the　bimetallic　center　play　different　roles　during　NRR　process,　in　which　Co　atom　does　not　directly　participate　in　the　binding　of　intermediates,　but　primarily　serves　as　a　reservoir　of　H　atoms.　This　special　synergy　makes　Co/alpha-MoC(001)　have　superior　activity　for　ammonia　synthesis.　The　introduction　of　Co　not　only　facilitates　N-2　dissociation,　but　also　accelerates　the　migration　of　H　atom　due　to　the　antibonding　characteristic　of　Co-H　bond.　This　study　offers　a　facile　strategy　for　the　rational　design　and　development　of　efficient　catalysts　for　ammonia　synthesis　and　other　reactions　involving　the　hydrogenation　processes.