A new type of heterojunction photocatalyst, Bi₂SiO₅/g-C₃N₄, was prepared using a controlled hydrothermal method. The structure and morphology of the Bi₂SiO₅/g-C₃N₄ photocatalyst were characterized by XRD, HR-TEM, FE-SEM-EDS, HR-XPS, FT-IR, PL, BET, EPR, and UV-Vis-DRS. The obtained Bi₂SiO₅/g-C₃N₄ photocatalyst exhibits enhanced photocatalytic activity on the decolorization of crystal violet (CV) under visible-light irradiation. In particular, the catalytic performance illustrates the best reaction rate constant of 0.1257 h⁻¹ using Bi₂SiO₅/g-C₃N₄ as the photocatalyst, which is 5 and 3 times higher than the reaction rate constants of Bi₂SiO₅ and g-C₃N₄ as photocatalysts, respectively. This study shows that Bi₂SiO₅/g-C₃N₄ can be used to suppress the recombination of photoinduced electron–hole pairs and contribute to the enhanced photocatalytic efficiency of semiconductors in the visible light-driven catalysis. The quenching effects of different scavengers, and EPR results demonstrate that the reactive O₂˙⁻ plays the major role and ˙OH, h⁺ and ¹O₂ play minor roles in CV degradation. The probable photodegradation mechanisms are proposed and discussed.