Pt-based　catalysts　are　commercial　electrocatalysts　for　the　hydrogen　evolution　reaction　(HER),　but　their　shortcomings　of　expensive　and　imperfect　efficiency　hinder　their　large-scale　application.　Here,　we　report　an　Ir-based　HER　catalyst　supported　by　N-doped　carbon　nanosheets　(Ir-NCNSs).　The　NCNSs,　with　a　high　surface　area　and　unique　atomic　composition,　enable　Ir　nanoparticles　(NPs)　to　disperse　at　2-3　nm　and　strongly　coordinate　to　the　Ir　through　Ir-N　bonds,　which　exposes　many　active　sites　and　strengthens　their　durability.　The　catalyst　displays　a　low　over-potential　and　a　small　Tafel　slope　of　46.3　mV　at　10　mA　cm(-2)　and　52　mV　dec(-1)　in　0.5　M　H2SO4,　respectively.　When　used　in　1.0　M　KOH,　Ir-NCNSs　also　show　excellent　electrocatalytic　activity　with　a　low　overpotential　of　125　mV　at　10　mA　cm(-2).　The　calculated　results　further　suggest　that　Ir　NPs　and　NCNSs　have　excellent　selectivity　for　strong　metal-support　interactions,　corresponding　to　a　significant　and　stable　HER　characteristic.　Our　findings　provide　insight　into　the　design　of　high-efficiency　Ir-based　HER　catalysts.