Abstract: Oxidized carbon nitride nanosheets (o-CN NSs) was prepared by oxidative stripping with bulk carbon nitride (CN) as the precursor, and then reduced carbon nitride nanosheet (r-CN NSs) was prepared via reduced o-CN NSs. The thickness of o-CN NSs and r-CN NSs are both about 2 nm and retain the heptazine ring skeleton structure of pure CN. Compared with o-CN NSs, r-CN NSs has a smaller band gap (2.62 eV), wider photoresponse range (485 nm) and higher H₂ evolution rates (1700 μmol/(g·h)). The H₂ evolution rates of r-CN NSs is 8.5 times of CN and 2.1 times of o-CN NSs. After a 20 h cycle test, the photocatalytic hydrogen production efficiency of r-CN NSs has no attenuation, has well photocatalytic stability. Experimental and theoretical analyses reveal that r-CN NSs is nanosheet structure with amino group at the edge. The introduction of amino group improves the crystallinity of nanosheets, improves the separation efficiency of electrons and holes, broadens the photoresponse range of nanosheets, thus resulting in the enhanced photocatalytic performance.