<p>In this work, CuO/Bi₃NbO₇ <i>p–n</i> heterojunction photocatalyst was designed and successfully prepared, in order to overcome the problems, such as high recombination rate of photo-generated carriers, limited light absorption range and so on. The resulted samples were characterized by techniques, such as XRD, SEM, TEM, UV–vis DRS, BET, electrochemical test. The visible light degradation performance for MB was investigated. The effects of CuO composite ratio, initial MB concentration, catalyst addition amount and pH on the catalytic activity were discussed. The experimental results showed that CuO nanoparticles were successfully loaded on Bi₃NbO₇, and the composite catalyst exhibited a loose and porous morphology. The combination of CuO not only improved the absorption capacity for visible light, but also promoted the transfer of photo-generated electrons and holes, and improved the photocatalytic activity of Bi₃NbO₇. Under the optimized experimental conditions, after visible light irradiation for 180&#xa0;min, the degradation efficiencies of MB and TC on CuO/Bi₃NbO₇ composite with 5 wt % CuO loading reached 96% and 99%, respectively, which were higher than that of bulk Bi₃NbO₇. This<i> p–n</i> heterojunction promoted the separation of photo-generated charges. It provides a reference for improving the photocatalytic activity of Bi₃NbO₇.</p>