In this study, vanadium dioxide (VO2) powder well known as a thermochromic material was prepared from V2O5 powder and oxalic acid dihydrate by hydrothermal and calcination process at various conditions. The chemical bonding and crystal structures in addition to thermal property of samples were determined using FE-SEM, XRD, XPS, and DSC. Also, spectroscopic and thermochromic properties of film samples were analyzed by UV-Vis-NIR spectroscopy after the thin film was prepared from the sol dispersed with the size of below 50 nm by the ball-milling of powder sample. With increasing the calcination temperature, the phase transition temperature of samples increased from 40 ℃ to 70 ℃ due to the increase of particle size. Keywords