Abstract: The heterojunction photocatalytic material constructed with g-C₃N₄ as the matrix shows excellent effects in degrading toxic and harmful pollutants. In this study, a series of x-CS/g-C₃N₄ (x=4wt%, 5wt% and 7wt%) composite photocatalysts with different addition amounts of carbon nanospheres (CS) were prepared by hydrothermal method, and the photocatalytic degradation performance of x-CS/g-C₃N₄ on acid orange II were explored when a xenon lamp was used as a visible light source. The results show that the photocatalytic activity of 5wt% CS/g-C₃N₄ is the highest, and the degradation rate of acid orange II reaches 95% when the photocatalytic reaction is 150 min. The characterization results show that g-C₃N₄ and CS have a similar π-π conjugate structure, and π-π stacking interaction is prone to occur, which is beneficial to electronic transition. The combination of g-C₃N₄ and CS can effectively enhance the absorption efficiency of g-C₃N₄ for visible light, reduce the charge transfer resistance at the surface/interface, and significantly enhance the transport capacity of carriers. x-CS/g-C₃N₄ can be used as an effective visible light catalyst for the degradation of organic dyes and has application prospects.