In the process of industrial production activities such as textile, printing and dyeing, coating and medicine, about 10%~15% of organic pollutants will be discharged into the surrounding water, soil and atmosphere with industrial wastewater, which increases the difficulty of organic dye treatment. Photocatalysis is considered to be one of the most promising technologies to solve the problems of energy shortage and environmental pollution in the future. It has been used to degrade organic pollutants. However, there are still many problems in the application of photocatalysts, such as low photon efficiency, high recombination rate of photoinduced electron hole pairs or poor stability. In order to expand the industrial application of photocatalytic technology, the modification of photocatalyst is an important direction to improve the utilization of solar energy. ZnO has the advantages of good photosensitivity, non toxicity, high electron mobility and low cost, but it is a wide band gap semiconductor, only responds to ultraviolet light, and the photon utilization is low. Bismuth oxyhalide BiOX (X=Cl, Br, I) has attracted extensive attention because of its special structure and excellent photocatalytic performance. As a typical bismuth halide oxide photocatalyst, BiOBr has a suitable band gap (2.61 eV), which makes it have the characteristics of good activity and stable photocatalytic performance under visible light irradiation. Therefore, it has become one of the materials that can not be ignored in the field of photocatalytic degradation of water pollution. However, the photocatalytic effect of pure BiOBr is poor. The combination of BiOBr and ZnO to form ZnO/BiOBr heterojunction can improve the photocatalytic activity of single component semiconductor photocatalytic materials and broaden the application range of ZnO and BiOBr. In previous studies, the binary composite ZnO/BiOBr was synthesized by hydrothermal method, and the dye degradation experiment was carried out to improve the photocatalytic degradation activity of single component. SHASHA Y et al. prepared ZnO/BiOBr complex by two-step hydrothermal method and showed excellent catalytic activity for the photodegradation of Methyl Orange (MO). GENG Y G et al. synthesized flower like ZnO/BiOBr by hydrothermal method, showing good photocatalytic degradation ability for Methyl Blue (MB). MENG X C et al. synthesized binary heterojunction ZnO/BiOBr by hydrothermal method. The photodegradation ability of Rhodamine B (RhB) was obviously better than that of single component. In previous studies, ZnO/BiOBr binary composites were synthesized by hydrothermal method, and some were synthesized by two-step method. This subject tried to synthesize ZnO/BiOBr with different morphology in one step by adding some ethylene glycol solvent. Although the photocatalytic activity could not be compared with previous studies due to different reaction conditions and degradation substrates, ZnO/BiOBr (1∶2) with high catalytic degradation activity was selected in this work. ZnO/BiOBr composite photocatalysts with different ratios of ZnO and BiOBr (1∶1, 1∶2, 1∶3, 2∶1, 2∶3, 3∶1 and 3∶2) were prepared. When the molar ratio of ZnO to BiOBr was 1∶2, the photocatalytic degradation performance of ZnO/BiOBr composite was the best. Under visible light for 120 min, the removal rate of Rhodamine B (RhB) (20 mg/L) was 98.89% and the degradation rate constant was 0.040 50 min^-1, which was 4 times that of pure BiOBr. The binary composites ZnO/BiOBr were detected through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution TEM, UV-vis diffuse reflection spectroscopy, photoluminescence analysis and electron spin resonance spectroscopy. X-ray diffraction analysis and transmission electron microscope analysis found that ZnO and BiOBr were successfully compounded. The scanning electron microscope analysis results showed that the the binary composite ZnO/BiOBr with different molar ratios showed flake structures of different sizes, and granular ZnO could not be seen on the surface of flake structures. Among them, the flake structure size of ZnO/BiOBr (1∶2) sample was the largest. UV-vis diffuse reflectance analysis showed that compared with pure ZnO, the band gap decreased significantly after BiOBr and ZnO were combined, indicating that the utilization range of spectrum was improved, which was beneficial to the improvement of photocatalytic performance. Photoluminescence analysis showed that the peak intensity of ZnO/BiOBr (1∶2) binary composite was between pure ZnO and BiOBr, indicating that the addition of BiOBr improved the utilization of photogenerated electrons and holes in pure ZnO. The results of reuse experiment showed that after repeatedly degrading Rhodamine B (RhB) 5 times, ZnO/BiOBr (1∶2) still maintained high activity, and the degradation rate of Rhodamine B decreased by 9%, indicating that the composite photocatalyst ZnO/BOBr (1∶2) had good stability. Electron spin resonance spectroscopy results showed that a large number of ·O₂^- and ·OH radicals were indeed produced in ZnO/BiOBr (1∶2) photocatalytic system. Therefore, it could be preliminarily concluded that ·O₂^- and ·OH radicals were important active species in ZnO/BiOBr (1∶2) photocatalytic reaction system. Combined with the theoretical analysis of semiconductor energy band, the existence of ·O₂^- and ·OH radicals was confirmed again, and the organics were degraded into small molecular substances through their oxidation. The photocatalytic degradation mechanism showed that the interface electric field was formed in the photocatalytic process of ZnO/BiOBr (1∶2) to inhibit the recombination of photogenerated electrons and holes. All results suggested that the ZnO/BiOBr (1∶2) composite with high photocatalytic degradation efficiency, excellent recyclability and stability can meet a potentially promising application for photocatalytic degradation of waste water.