Faced with the growing consumption of fossil fuels and the consequent energy/ecological crisis, photocatalysis has become a realistic option to develop new energy source and realize the carbon neutrality. Heterojunction photocatalysts constructed by multiple semiconductors with staggered band structure can spatially separate redox reaction sites to realize synergistic oxidation and reduction reactions, and have captured broad interest. However, the undesigned heterojunctions still encounter some headache difficulties, that is the poor interfacial contact, which will block carrier mobility, thus result in inefficient and instable catalysts. Recently, researchers have been focusing on constructing chemical bonds (especially covalent bonding) between different semiconductors to induce the formation of intimate and stable interface contact. Herein, this review article presents the state-of-the-art progress on interfacial chemical bonds (ICB) in heterojunction photocatalysts and clarifies the function mechanism for enhancing photocatalysis. Given that the formation of ICB strongly depends on the surface characteristics of semiconductors, we clarify the formation mechanism and put forward rational design strategies. More importantly, the current photocatalytic applications of ICB are reviewed to have a deep understanding of structure–activity related mechanisms. Finally, our brief outlooks on the current challenges and future development trends of ICB for next-generation photocatalysts are pointed out to create brand-new strategies for optimizing photocatalytic properties and accelerate the practical applications of ICB with high-performance.