Abstract: In recent years, researchers have proposed a new S-scheme heterojunction photocatalyst, which has distinct advantages in the effective separation of photogenerated electron-hole pairs, recombination of useless electrons and holes, high separation efficiency of charge carriers, and retention of strong oxidation reduction active sites. In this paper, the reaction mechanism and preparation method of S-scheme heterojunction photocatalyst and the research progress of its application in water decomposition to produce hydrogen, CO₂ reduction, and the degradation and sterilization of pollutants have been summarized. Finally, prospects and challenges for the development of S-scheme photocatalytic systems are presented.