<p>The photocatalytic activity of g-C₃N₄ is largely limited by its high aggregation and the rapid recombination of photogenerated electron–hole pairs. In this study, Bi and La were co-loaded on g-C₃N₄ by NaBH₄ reduction method, and Bi/La/g-C₃N₄ composite photocatalyst with good visible light catalytic activity was synthesized. The composition and morphology of the composite were characterized by SEM, TEM, XRD and XPS. Under the irradiation of 70 W metal halide lamp, the degradation ability of Bi/La/g-C₃N₄ for Rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and tetracycline hydrochloride (TC) was investigated. The results show that Bi/La/g-C₃N₄ has a strong photocatalytic degradation ability for RhB, MB and TC, and also has a certain degradation ability for MO. After irradiation with a 70 W metal halide lamp for 30 min, RhB can be almost completely degraded. DRS, PL and EIS tests indicate that the outstanding photocatalytic performance of the Bi/La/g-C₃N₄ composite can be attributed to its stronger visible light absorption capacity, lower photogenerated electron–hole pair recombination rate and higher photogenerated carrier mobility. The Bi/La/g-C₃N₄ composite demonstrated remarkable stability and reusability. The main active species in its photocatalytic system are superoxide radicals (·O₂⁻) and holes (h⁺), while hydroxyl radicals (·OH) play a secondary role. It provides a promising approach for the preparation of efficient g-C₃N₄ composite photocatalysts for the treatment of organic wastewater.</p>