Two-dimensional　polymeric　carbon　nitride　(PCN)　nanosheets　have　evoked　considerable　attention　as　functional　photocatalyst　with　unique　physicochemical　properties　and　potentials　in　the　applications.　Despite　significant　advances　in　the　fabrication　of　PCN　nanosheets,　it　remains　a　considerable　challenge　to　prepare　PCN　nanosheets　by　an　inexpensive　and　high-yield　method.　Here　we　illustrated　a　new　effort　to　synthesize　PCN　nanosheets　by　adding　reusable　ammonia　decomposition　catalyst　in　the　thermal　condensation　process.　The　melamine　was　used　as　the　precursor,　which　will　slowly　release　ammonia　during　thermal　polymerization.　The　industrial　catalyst　(Z204,　Ni　species　as　active　component　on　Al2O3)　is　used　to　decompose　ammonia　then　promote　the　sluggish　ammonia　release　during　the　polymerization,　leading　to　the　successful　fabrication　of　holey　carbon　nitride　nanosheets　(CNS).　The　resultant　holey　CNS　exhibits　a　higher　Brunauer-Emmett-Teller　(BET)　surface　area,　which　is　15.8　folds　of　bulk　PCN.　The　enlarged　BET　surface　area　with　more　exposed　active　edges　and　sites,　and　significantly　promoted　charge　transfer　ability,　combining　with　a　stronger　thermodynamic　driving　force,　led　to　a　remarkably　boosted　solar　driven　H-2　evolution　performance.