The graphitic carbon nitride has been widely used in energy and environmental protection owing to its excellent properties. This paper discussed the mechanism and the preparation and modification methods of graphitic carbon nitride. In addition, its applications in both pollutant removal and detection were reviewed, such as the degradation of organic pollutants, reduction of heavy metal ions and the inactivation of microorganisms. Then, it introduced the development of some photocatalytic coupling technologies of graphitic carbon nitride in water treatment. It maintains the graphitic carbon nitride application in the future is prospective, especially in the direction of preparation methods optimization, recovery efficiency improvement and combination with other technologies.