N-Doped porous g-C 3 N 4 nanosheets for high-efficiency photocatalytic water splitting were prepared by mixing the precursor of N , N -dimethylformamide and urea through a simple one-step thermal copolymerization method. In this work, layered N-doped graphitic carbon nitride (g-C 3 N 4 ) porous nanosheets were successfully prepared by mixing the precursor of N , N -dimethylformamide (DMF) and urea through a simple one-step thermal copolymerization method. The doped-N plays a significant role in modifying the chemical and electronic structure of g-C 3 N 4 , which can decrease the migration pathway of the charges and suppress the recombination of the photogenerated carriers based on experimental characterization data and the density functional theory (DFT) calculation results. Through nanostructure engineering design, the as-prepared photocatalyst exhibits promoted specific surface area and enhanced light absorption capacity. Consequently, the as-prepared N-doped porous g-C 3 N 4 nanosheets yield about 14 times higher H 2 evolution rate than pristine g-C 3 N 4 nanosheets under visible light irradiation. The present study provides a simple and convenient method of nanostructure engineering for the synthesis of modified g-C 3 N 4 with excellent photocatalytic activity to meet the sustainable demand of energy.