Bismuth chloride oxide is a potential photocatalyst with a unique structure and visible light responsive properties. This paper explores the effects of different ratios of NiO on the photocatalytic performance of NiO/BiOCl heterojunction photocatalysts, which are prepared by impregnation and annealing. The experimental results demonstrate that the construction of NiO/BiOCl heterojunction enhances the visible light response and significantly decreases the compounding efficiency of the photogenerated carriers. The degradation of tetracycline by 6% NiO/BiOCl was almost complete within approximately 30 min, which is about 30% faster than that of unmodified BiOCl. The cycling performance is excellent and the preparation process is simple, making it highly applicable.