Two dimension layered BiOX (X=Cl, Br, I) semiconductor nanomaterials are very important photocatalysts. Our previous work showed that thickness-ultrathin and bismuth-rich strategies are excellent methods to improve the visible-light-driven (VLD) photocatalytic reduction activity of BiOX. In this study, thickness-ultrathin and bismuth-rich strategies were ingenuously combined to enhance the photocatalytic performance of the photocatalyst, via a glycerol precursor route, Bi4O5Br2 microsphere assembled by ultrathin nanosheets was synthesized and characterized by X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), time-resolved PL spectra and UV-vis diffuse reflectance spectra (DRS). The thickness of Bi4O5Br2 ultrathin nanosheets was about 3.7 nm, which was much thinner than the common BiOBr nanosheets (65 nm). Due to the thickness-ultrathin and bismuth-rich strategies, the synthesized Bi4O5Br2 sample displayed a higher photocatalytic reduction activity of CO2 conversion than BiOBr and ultrathin BiOBr under visible-light irradiation. More importantly, we found that thickness-ultrathin and bismuth-rich strategies played different roles. Thickness-ultrathin strategy only can increase the CO generation while bismuth-rich strategy only can increase the CH4 generation for photoreduction of CO2. (C) 2016 Elsevier B.V. All rights reserved.