Recently, bismuth oxyhalide photocatalysts have attracted much attention owing to their unique layered structure. In this paper, fluorine isomorphously substituted BiOBrxI1-x solid solution was synthesized by controlling the molar ratios of F, Br and I elements by the chemical precipitation method at room temperature. It was found that BiOF0.4Br0.5I0.1 exhibited excellent photocatalytic activity for the degradation of methyl orange, which was 10.1, 5.0 and 4.3 times higher than that of BiOI, BiOBr and BiOBr0.9I0.1 under visible light irradiation, respectively. It could be inferred that fluorine substitution is favorable to enhance the internal electric field (IEF) for BiOBrxI1-x with layered structure, which could improve the separation efficiency of the photogenerated holes and electrons and thus enhance the photocatalytic activity. On the other hand, the concentration of oxygen vacancies (OVs) rose with the increase of fluorine content, which could facilitate the adsorption of pollutants and serve as trapping sites for photo-induced carriers to improve the photocatalytic activity. The finding provides new insights into the synergistic effect of IEF and OVs toward the construction of high efficient photocatalysts. (C) 2019 Elsevier Inc. All rights reserved.