Two-dimensional　electride　Ca2N　has　strong　electron　transfer　ability　and　low　work　function,　which　is　a　potential　candidate　for　hydrogen　evolution　reaction　(HER)　catalyst.　In　this　work,　based　on　density　functional　theory　calculations,　we　adopt　two　strategies　to　improve　the　HER　catalytic　activity　of　Ca2N　monolayer:　introducing　Ca　or　N　vacancy　and　doping　transition　metal　atoms　(TM,　refers　to　Ti,　V,　Cr,　Mn,　Fe,　Zr,　Nb,　Mo,　Ru,　Hf,　Ta　and　W).　Interestingly,　the　Gibbs　free　energy　ΔGH∗　of　Ca2N　monolayer　after　introducing　N　vacancy　is　reduced　to　-0.146　eV,　showing　good　HER　catalytic　activity.　It　is　highlighted　that,　the　HER　catalytic　activity　of　Ca2N　monolayer　can　be　further　enhanced　with　TM　doping,　the　Gibbs　free　energy　ΔGH∗　of　single　Mo　and　double　Mn　doped　Ca2N　are　predicted　to　be　0.119　and　0.139　eV,　respectively.　The　present　results　will　provide　good　theoretical　guidance　for　the　HER　catalysis　applications　of　two-dimensional　electride　Ca2N　monolayer.　©　2023