Visible-light-induced BiVO4 microspheres with different crystalline phases have been successfully synthesized via simple thermal treatment methods. The photocatalytic activities of the samples were evaluated by the degradation of methylene blue (MB) under visible-light irradiation (420 nm < lambda < 800 nm). The results indicated that the BiVO4 sample prepared at 400 degrees C, which was composed of mixed crystalline phases (tetragonal and monoclinic BiVO4), exhibited the best activity. Through the detection of the degradation mechanism, it was found that the mixed phases availed the transfer of electrons and led to the generation of more kinds and amount of active species in the degradation process. The active species enhanced the photocatalytic activity. These results would be useful to develop highly efficient photocatalysts and helpful to reveal the degradation mechanism clearly. (C) 2016 Elsevier Ltd. All rights reserved.