Abstract: As a widely used antibiotic, tetracycline exists in water environment for a long time and is difficult to be degraded naturally, which does great harm to ecological environment and human health. BiOI and Bi₂O₃/BiOI photocatalysts were prepared by simple room temperature stirring method and solvothermal method. The morphology and structure of the materials were characterized by XRD, SEM, FTIR, UV-Vis, PL and EIS. The effects of different preparation conditions on the degradation of tetracycline by Bi₂O₃/BiOI composite photocatalytic material under simulated sunlight were investigated. The results show that when the molar ratio of Bi₂O₃ to BiOI is 0.8∶1, the reaction pH is 5, the reaction temperature is 180℃, the reaction time is 20 h, the composite photocatalytic material has the best degradation effect on tetracycline, which can reach 75% in 3 h. And the kinetic rate constants are 1.75 times and 1.56 times of that of single BiOI and Bi₂O₃, respectively. A catalytic mechanism of binary heterojunction photocatalyst is proposed to explain the improved photocatalytic activity.