Highly orientated V2O5 thin films were prepared by sol-gel method on SiO2/Si substrate, The thin films of V2O5 were found converting to VO2 thin films under a temperature above 400 degreesC and a pressure below 2 Pa in air. It was observed that the reduction process follows the sequence as V2O5 --> V3O7 --> V4O9 --> V6O13 --> VO2, namely from VnO2n+1 (n = 2-4,6) to VO2. Annealing the V2O5 thin film at 480 degreesC, under 1-2 Pa for 20 min, the VO2 polycrystalline thin film with the resistivity change larger than 3 orders through the transition temperature was obtained, The transition temperature was influenced by the heating condition in vacuum. (C) 2002 Elsevier Science B.V. All rights reserved.