Bi2WO6-Bi composite was synthesized by in situ photoreduction of Bi2WO6. Bi2WO6-Bi exhibits improved photocatalytic efficiency towards degradation of Rhodamine B. The generation of elemental Bi in Bi2WO6-Bi induces vacancy and structure distortion of Bi2WO6. The surface oxygen adsorption mode changes from hydroxyl group on Bi2WO6 to molecular oxygen on Bi2WO6-Bi.