Various photocatalysts have been fabricated and tested for the treatment of water and wastewater. As visible light-driven photocatalysts, bismuth oxybromide nanomaterials have weak responses to visible light and low activities of using photogenerated h(+) to produce hydroxyl radicals (center dot OH), both of which are limited by their band structures. Thus, modification of bismuth oxybromide to form an optimized band structure is essential to enhance its photocatalytic activity for environmental applications. In this work, an oxygen-rich bismuth oxybromide nanomaterial, Bi24O31Br10 nanobelt, was fabricated using a solvothermal method, which possessed a narrower band gap and a more positive position of valance band top. As a result, this catalyst exhibited a strong response to visible light and produced large quantities of center dot OH directly via its photogenerated h(+), which contributed to the outstanding performance of photocatalysis, as evidenced by the experimental results and density functional theoretical (DFT) calculations. Under visible light irradiation, the Bi24O31Br10 nanobelt exhibited a substantially enhanced photocatalytic efficiency for the degradation of bisphenol A compared to those of Bi24O31Br10 and BiOBr nanosheets. Moreover, this catalyst could resist most interfering ions and was able to treat two types of actual industrial wastewaters efficiently. This work elucidates a new approach to modify photo catalysts and is helpful to expand practical applications of photocatalytic technologies for water and wastewater treatment.