Hydrogen evolution by photocatalytic technology has been one of the most promising and attractive solutions, and can harvest and convert the abundant solar energy into green, renewable hydrogen energy. As a new kind of photocatalytic material, graphitic carbon nitride (g-C₃N₄) has drawn much attention in photocataluytic H₂ production due to its visible light response, ease of preparation and good stability. For a higher photocatalyic performance, N defects were introduced in to the traditional g-C₃N₄ in this work. The existence of N defects was proved by adequate material characterization. Significantly, a new absorption region at around 500 nm of N-deficient g-C₃N₄ appeared, revealing the exciting n-π* transition of lone pair electrons. The photocatalytic H₂ production performance of N-deficient g-C₃N₄ was increased by 5.8 times. The enhanced photocatalytic performance of N-deficient g-C₃N₄ was attributed to the enhanced visible light absorption, as well as the promoted separation of photo-generated carries and increased specific surface area.