Abstract: The construction of surface plasmon resonance (SPR), oxygen vacancies, and heterojunctions is one of the effective ways to enhance the catalytic activity of semiconductor photocatalysts. In this paper, Bi-Bi₂O₃-BiOBr ternary heterojunction composites with SPR effect and oxygen vacancies were synthesized by a one-step solvothermal method by changing the molar ratio of Bi(NO₃)₃ to KBr. Used XRD, electron paramagnetic resonance (EPR), XPS, SEM, TEM, UV-vis and other means to characterize and analyze the crystal phase, elemental composition and microscopic morphology of the obtained product, and investigate the effect of the molar ratio of Bi(NO₃)₃ to KBr on the visible light-driven photocatalytic degradation of methylene blue (MB) activity of the ternary complex. The results show that the catalytic activity of Bi-Bi₂O₃-BiOBr depends on the molar ratio of Bi(NO₃)₃ to KBr, but is higher than that of pure Bi₂O₃ and BiOBr. The 2∶1-Bi-Bi₂O₃-BiOBr prepared with a molar ratio of Bi(NO₃)₃ to KBr of 2∶1 exhibited the best photocatalytic activity towards MB. 2∶1-Bi-Bi₂O₃-BiOBr was irradiated with visible light for 240 min. The removal rate of MB on Bi-Bi₂O₃-BiOBr is 95.07%, and the degradation kinetics conform to pseudo-first-order kinetics. The degradation rate constant is 2.90 h⁻¹, which is 5 and 6 times that of pure Bi₂O₃ and BiOBr, respectively. After 4 cycles of experiments, 2∶1-Bi-Bi₂O₃-BiOBr composite does't significantly reduce the removal efficiency of MB. The excellent visible-light photocatalytic activity of this material can be attributed to the three synergistic effects of SPR effect, semiconductor heterojunction structure and oxygen vacancies. The method for synthesizing photocatalysts with special structures in this paper can be extended to other catalytic materials.