As a classic non?metallic semiconductor photocatalyst, graphite phase carbon nitride material （g?C₃N₄） has attracted widespread attention in recent years due to its stable physical and chemical properties, reasonable band structure, low cost, easy availability, safety, and pollution?free advantages. It has good application and development prospects in the fields of environmental protection, purification and energy catalysis. However, the utilization of g?C₃N₄ in studies is significantly hampered by its tiny specific surface area, limited absorption of visible light, and high rate of recombination of photogenerated electrons and holes. The basic structure, characteristics and main modifications of g?C₃N₄ are reviewed, covering modification means such as elemental doping, morphological modulation, noble metal deposition and the practical applications of g?C₃N₄ in recent years at home and abroad.