Vanadium oxide is a promising material due to its thermochromic characteristics and is currently being evaluated for use in various thermal and optical applications. VO₂ films were prepared on quartz substrates using the sol-gel method, spin coating, and annealing. To obtain VO₂ films with high purity and improve their thermochromic properties, the effect of the annealing temperature on the film’s structure and properties was investigated. As the annealing temperature increased from 450 °C to 650 °C, the film’s phase component went through an amorphous phase, a VO₂ phase with initial crystallization, a VO₂ phase with high purity and mature crystallization, a VO₂ phase with a small amount of a V₂O₅ phase, and a VO₂ phase with a greater amount of a V₂O₅ phase. The film’s crystallinity improved continuously, and the film annealed at 550 °C was composed of fine, compact particles; higher temperatures resulted in coarser grains. The maximum transmittance mutation of the film to infrared radiation first increased and then decreased. The film annealed at 550 °C attained the maximum value of 67% at a wavelength of 2500 nm, and its phase transition temperature was 67.6 °C.