Three-dimensional (3D) Bi2O3-BiOI heterojunction was fabricated on the basis of Bi2O3 film by a simple dipping method at room temperature. The as-prepared film samples were characterized by scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis DRS spectra. Results indicated that BiOI nanosheets with cross-flake arrays were formed via in situ etching and exchanging of Bi2O3 layer by I- in XI aqueous solution, which grow around the residual Bi2O3 particles to form 3D Bi2O3-BiOI heterojunction. Liner sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) Nyquist plots and incident monochromatic photon-to-current conversion efficiency (IPCE) indicated' that easier generation, separation and transfer of photogenerated charges were achieved on the special 3D heterojunction. The photocurrent density of the 3D Bi2O3-BiOI composite increased by 8.4 times relative to pure Bi2O3 at 0.35 V vs. AgIAgCl in 0.2 M Na2SO4 aqueous solution under visible light irradiation. For the PEC degradation of phenol, the composite film also exhibited greatly enhanced activity. The calculated rate constant was 3.8 times that on pure Bi2O3. Furthermore, good stability in long-time photocurrent and cyclic degradation of phenol can both be observed, indicating that the 3D Bi2O3-BiOI film can be potentially applied in water oxidation and environmental remediation. (C) 2016 Elsevier B.V. All rights reserved.