Increasing organic pollutants have seriously affected the ecological environment and human health, photocatalytic technology is considered as one of the most effective and environmentally friendly treatment methods. In this work, a novel hierarchical polyurethane (PU)/reduced graphene oxide (RGO)/bismuth oxyiodide (BiOI) composite fiber photocatalyst is constructed via an energy-saving route consisted of ultrasonic-assisted and co-precipitation method by utilizing PU nanofibers as substrate. The RGO are first evenly wrapped in the PU nanofiber surface and BiOI nanosheets are then uniformly grown on the PU/ RGO surface to form the hierarchical PU/RGO/BiOI composite fibers with a core–shell structure. The composition, morphology and electrochemical performance of the obtained PU/RGO/BiOI were characterized by XRD, XPS, SEM, BET, I-t and EIS. Benefited from the high specific surface area of the PU nanofiber and the excellent electron transfer ability of the RGO, a remarkable photocatalytic activity was achieved for the PU/RGO/BiOI composite fibers and the degradation rate of RhB is 93.2% within 180 min. Notably, compared to the traditional suspended nanoparticles, the PU/RGO/BiOI fibers exhibit excellent flexibility and self-supporting property, and can be easily separated and recovered from the contaminated water. Thus, the obtained PU/RGO/BiOI composite fibers with high photocatalytic activity and easily separable property are expected to possess great potential in water purification.