In this paper, we report the preparation of thermochromic porous nano-structured VO2 films. The films with sphere-shaped, stone-shaped, and rod-shaped particles were derived from a sol-gel process with inorganic precursor and polyethylene glycol (PEG). The obtained porous nano-structured VO2 films show tiny particles (about 20 nm), excellent optical property (light switching efficiency of 67%), and controlled hysteresis loop features (width and slope). The films can be obtained by simply controlling the N-2 flow rate during annealing process, providing an effective process for growing high quality thermochromic porous nano-structured VO2 films with controllable hysteresis features, which is of great importance in achieving practical application. (c) 2013 Elsevier Ltd. All rights reserved.