The　electrochemical　acetonitrile　(CH3CN)　reduction　reaction　is　a　promising　route　to　produce　ethylamine　(CH3CH2NH2)　under　ambient　conditions,　but　lacks　efficient　catalysts.　The　metal-free　catalysts　were　rarely　re-ported　in　current　studies　with　the　focus　of　metal-based　materials.　Here,　we　demonstrated　that　the　metalloid　boron　atom　can　act　as　the　highly　active　site　for　the　reaction　via　density　functional　theory　(DFT)　computations.　Using　experimentally　accessible　C2N　monolayer　as　substrate,　three　boron　doped　catalysts,　namely　B/C2N,　were　built,　which　show　excellent　thermodynamic　and　dynamic　stability,　high　selectivity　and　effective　poison　resis-tance　function　toward　CH3CN　reduction　reaction.　The　B/C2N　can　effectively　capture　and　activate　CH3CN　molecule　via　the　electron　＂donation/back-donation＂　process.　Especially,　boron-embedded　C2N　(Bint/C2N)　pos-sesses　the　highest　catalytic　performance　with　the　lowest　limiting　potential　of-0.11　V.　Further　electronic　property　analyses　demonstrated　Bint/C2N　has　superior　electrical　conductivity　and　smallest　work　function,　which　is　beneficial　to　the　electron　transfer.　This　work　provides　a　theoretical　guidance　for　the　construction　of　novel　and　high-efficiency　metal-free　electrocatalysts　towards　the　CH3CN　reduction　reaction.