This review article focuses on the advancements in alloying engineering for BiOX (bismuth oxyhalides) photocatalysts, addressing their unique layered structure and inherent limitations such as an inappropriate band gap and low carrier separation efficiency. The authors highlight how alloying engineering can optimize these intrinsic properties by tuning the halogen layers, enhancing the energy band structure, and improving carrier behavior. Various modification methods, including defect engineering, morphology control, bismuth-rich strategies, cation doping, heterojunction construction, and plasma resonance effects, are discussed. The applications of alloyed BiOX in energy and environmental fields, such as contaminant degradation, antibacterial, CO₂ reduction, nitrogen fixation, and organic synthesis, are also summarized. Finally, the challenges and future directions for alloyed BiOX are outlined, emphasizing the potential for further research and development in this area.This review article focuses on the advancements in alloying engineering for BiOX (bismuth oxyhalides) photocatalysts, addressing their unique layered structure and inherent limitations such as an inappropriate band gap and low carrier separation efficiency. The authors highlight how alloying engineering can optimize these intrinsic properties by tuning the halogen layers, enhancing the energy band structure, and improving carrier behavior. Various modification methods, including defect engineering, morphology control, bismuth-rich strategies, cation doping, heterojunction construction, and plasma resonance effects, are discussed. The applications of alloyed BiOX in energy and environmental fields, such as contaminant degradation, antibacterial, CO₂ reduction, nitrogen fixation, and organic synthesis, are also summarized. Finally, the challenges and future directions for alloyed BiOX are outlined, emphasizing the potential for further research and development in this area.