BiVO4/WO3 heterojunction film is considered as a very promising candidate for photoelectrochemical water splitting. However, the BiVO4/WO3 films prepared by a conventional method exhibit numerous grain boundaries in the BiVO4 layer and a weak contact at the heterojunction interface. In this paper, we found that BiVO4 could be formed from hydrothermal Bi2WO6 in the weak acid solution dissolving V2O5 and successfully developed an in situ transformation method to prepare BiVO4/WO3 heterojunction films. The prepared BiVO4/WO3 heterojunction films were characterized in detail and showed a high quality core/shell WO3/BiVO4 structure. The formation mechanism of the BiVO4 layer on the surface of WO3 film has been put forward. In particular, the prepared BiVO4/WO3 films were used as photoanodes and showed an excellent visible light response, a good photostability and high photoelectrochemical activity. The photocurrent density for BiVO4/WO3 photoanode was up to 2.92 mA cm(-2) at 1.81 VRHE without additional electrocatalyst or doping under visible light illumination. (C) 2017 Elsevier B.V. All rights reserved.