Graphite phase carbon nitride（g-C₃N₄） was prepared by thermal polymerization using melamine as precursor.Then bismuth oxyiodide（BiOI） was in-situ generated on its surface to construct BiOI/g-C₃N₄ composite.The catalyst was characterized by X-ray diffraction XRD,fourier transform infrared spectroscopy（FT-IR） and ultraviolet visible diffuse reflectance spectroscopy（UV-Vis-DRS）.The results showed that when the mass-of-substance of BiOI to g-C₃N₄ was 0.5,the catalyst of BiOI/g-C₃N₄ had high dispersion of BiOI particles and moderate band gap and the adsorption and degradation performance of methyl orange was the best.The catalyst of BiOI/g-C₃N₄ prepared at reflux temperature of 120 ℃ had moderate particle size,specific surface area and surface hydroxyl concentration and the best adsorption and degradation performance of methyl orange.In addition,the catalyst had good recyclability.