An ultrasound-assisted solvent substitution method was first developed to synthesize monoclinic scheelite (s-m) BiVO4. The BiVO4 (s-m) crystals exhibited flower-like and hierarchical dendrite morphologies and a far higher photocatalytic activity than that made by solid-state reaction for degradation of rhodamine B under visible light. This novel ultrasound-assisted solvent substitution method should be extendable to other materials.