Vanadium dioxide undergoes a reversible phase transition at approximately 68 ℃,and it is accompanied with drastic changes in its electrical and optical properties. It is difficult to get the accurate analytic expression dependent on temperature and wavelength through theoretical derivation,because phase transition mechanism is complex. Dispersion theory for refractive index and extinction coefficient of the vanadium dioxide thin film is studied,and its temperature-dependence dispersion formula of optical constants is presented by numerical fitting with Sellmeier dispersion model. By film matrix theory,the optical transmittance and reflectivity at different temperatures and wavelengths are calculated. In the use of magnetron sputtering,vanadium dioxide thin films of different thicknesses are deposited on glass,sapphire and silicon dioxide substrates. The optical transmittance and reflectivity of the films are measured,and the experimental curve agrees well with that of simulation.