An ethylene glycol/water (EG/H2O) system has been designed to synthesize monoclinic BiVO4 submicrospheres through a mild dodecylamine-assisted hydrothermal method. The results show that the crystal phase of the synthesized product can be tuned by changing the volume ratio of EG/H2O. Moreover, the effects of dodecylamine on the morphologies of the obtained products were also discussed. The photocatalytic activities of samples were evaluated on the degradation of methylene blue (MB) under visible-light irradiation (λ > 400 nm). The results indicated that BiVO4 submicrospheres exhibited better photocatalytic activities than peanut-shaped BiVO4.