Abstract: Aiming at the problems of low response efficiency of g-C₃N₄ to visible light and low separation efficiency of photogenerated electron-hole, a method of loading semiconductors onto the surface of g-C₃N₄ is proposed, which can improve the application of g-C₃N₄ in the photocatalytic degradation of organic pollutants. NiO/Fe₂O₃/g-C₃N₄ composites were synthesized by immersion method, and characterized by XRD, FT-IR and PL. The research results show that the degradation rate of OTC can reach 89.1% under photo-Fenton system. After the addition of TEOA, the degradation efficiency of OTC solution decreased from 89.1% to 42.1%. It can be concluded that hole （h⁺）, superoxide radical （·O₂⁻） and hydroxyl radical （·OH） were the main factor affecting the degradation process of OTC. NiO/Fe₂O₃/g-C₃N₄ photocatalytic composites have good photocatalytic degradation effect on OTC solution because double-S Scheme heterojunction formed between Fe₂O₃, NiO and g-C₃N₄ semiconductor can effectively separate electrons and holes and inhibit electron hole recombination. The research conclusion provides a reference for the application of heterojunction catalysts in conjunction with photo-Fenton in wastewater treatment.