This paper describes a solution-based route to synthesize vanadium dioxide (VO 2 ) thermochromic thin films on glass substrate by spin-coating technology followed by nitrogen-annealing with vanadium pentoxide (V 2 O 5 ) and oxalic acid (H 2 C 2 O 4 ) as source material, which is fairly economical and practical. Surface morphologies indicate that the films obtained by this method are homogeneous and particulate, irregular prisms emerge as the annealing temperatures increase. X-ray diffractions show that films annealed at relatively low temperature are pure monoclinic phase with a preferred orientation of (011). NaV 4 O 7 and NaV 6 O 15 form along with raising the heating temperatures. VO 2 films obtained exhibit excellent visible transparency and switching property at near-infrared wavelengths across the metal–semiconductor transition. Transmittance change at λ=2000nm of VO 2 thin film annealed at 450°C attains as high as 41.5% and its solar modulation efficiency reaches up to 8.8%. The W-doped VO 2 film at a doping level of 1at.% exhibits a thermochromic switch at 37°C with a narrow hysteresis, which will greatly favor the practical application of VO 2 -based smart windows.