Abstract: Semiconductor photocatalytic materials have become a key factor of photocatalytic technologies to solve environmental pollution and energy crisis. Among them, graphitic phase carbon nitride (g-C₃N₄) has shown great potential for application as an emerging highly efficient catalytic material. However, the unmodified g-C₃N₄ has disadvantages such as limited visible light response range, less reactive sites and high photogenerated carrier complexation rate, which severely limit its practical applications. Thus, researchers have adopted various strategies, such as designing and developing heterogeneous structures, defect engineering and morphological modulation to solve the problems mentioned above. Among them, defect modulation has attracted much attention because it can effectively modulate the electronic band structure of photocatalytic materials, delay carrier recombination and increase the surface reactive sites. This paper describes the types of defect modulations, defect modulation strategies, and finally summarizes the development and application of g-C₃N₄ based photocatalytic materials and gives an outlook.