Global environmental pollution and energy shortage are becoming increasingly prominent and have a significant impact on the living space of human beings. At present, the researches on photocatalytic semiconductor materials in photocatalytic degradation of organic pollutants in wastewater have attracted much attention from scholars at home and abroad. Ta2O5 has been proved to have higher photocatalytic activity than TiO2, so it is recognized as a photocatalytic material with great application prospects. Graphite-like carbon nitride is characterized by its large specific surface area, good adsorption, good chemical stability, high electron conductivity, and narrow band gap width (2.7eV). Therefore, the composite of g-C3N4?Ta2O5 and Fe3O4 photocatalytic materials based on the modification mechanism of semiconductor composite technology will be conducive to expanding the visible light response range, improving the quantum efficiency and enhancing the visible light catalytic performance. The poor dispersion and repetition stability of the materials prepared by the above method affect the catalytic performance of the composites. Proposed in this paper one step of hot solvent was prepared with different contents of g-C3N4 composite photocatalytic materials, based on the analysis of the structure and morphology of the composite photocatalytic materials, research sulphonamide wastewater in visible light catalytic degradation, analysis of the different content of g-C3N4 effect on the photocatalytic properties of the composite material, and further study of mechanism of photocatalytic decomposition of photocatalytic materials. Composite photocatalytic materials with visible light photocatalytic activity were prepared by thermal solvent method. The main results are as follows: a) The composite photocatalyst has a hollow spherical structure. The results of ultraviolet-visible diffuse reflectance show that the composite photocatalyst has a certain visible light response characteristics. b) The photocatalytic activity of the composite photocatalyst for the degradation of sulphonamide wastewater was tested. The results showed that the photocatalytic activity of the composite photocatalyst was the best when the light time was 120min and the content of g-C3N4 was 40wt%, and the degradation rate reached 99.8%. c) The photocatalytic degradation mechanism of the composites was further studied by capturing the active species. The results showed that superoxide radicals were the main active species. The cyclic photocatalytic experiments showed that the photocatalytic activity of the composites was stable under visible lightirradiation.