Abstract: Reduced graphene oxide (rGO)/TiO₂/BiOI ternary composites with different Bi/Ti molar ratios were prepared by a hydrothermal method. Their photocatalytic activities were investigated using methyl orange as a simulated pollutant. SEM, XRD, UV-vis diffuse reflectance spectroscopy, XPS and electrochemical tests were used to characterize their microstructures, light absorption properties and the mobility of photogenerated carriers. Results show that under visible light irradiation, the rGO/TiO₂/BiOI composite with a Bi/Ti molar ratio of 80% exhibits a highest degradation rate of 98% for methyl orange within 20 min. The TiO₂ nanoparticles are uniformly attached to BiOI nanosheets that are stacked on rGO sheets to form a heterostructure. The heterostructured rGO/TiO₂/BiOI has strong visible light absorption, which improves the separation efficiency of the photogenerated carriers and accelerates the carrier migration rate, thus increasing the photocatalytic activity of the catalyst.