In the present work, Bi/BiOI composite materials with multi-morphology and efficient photocatalytic performance have been synthesized by one-step chemical solvothermal method. At the same time, we have studied the solvothermal temperature, reaction time, and iodine source that affected the chemical compositions, crystallinity, morphology, and photocatalytic performance of synthesized Bi/BiOI composite materials. Our results suggest that Bi/BiOI composites with flower-like structures were prepared at 180 °C for 24 h (BiOI-180-24) under the presence of ionic liquids 1-butyl-3-methylimidazolium iodide ([EMIM]I), which exhibited higher photocatalytic performance toward Rhodamine B (RhB) under visible light irradiation, the possible reason was that Bi/BiOI had a moderate specific surface area and Eg. Moreover, experimental studies of free radical capture confirmed that holes are important active free species, leading to the degradation of dye molecules during irradiation.