The novel tungsten trioxide flocky microspheres induced by ethanol were successfully obtained via a simple and convenient hydrothermal route. The as-prepared products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy. BET surface area measurement and UV-Vis diffuse reflectance spectroscopy. WO3 powder prepared with volume ratio (v(ethanol)/v(water)) of 40% revealed a complete flocky microsphere structure with particle size of 3.0-4.0 mu m and exhibited good photochromic property. The possible formation mechanism of the flocky microspheres was proposed and the improved photochromic properties were also investigated. (C) 2011 Elsevier B.V. All rights reserved.