Vanadium dioxide (VO2) have attracted tremendous interest in recent years due to their semiconductor-metal transition near room temperature. In this work, we report numerical simulation of the optical properties of VO2 thin layers which include the index of refraction, the coefficient of extinction, the reflectance and the transmittance. In this sense, we used the Model of Drude-Lorentz for calculating coefficients at from the optical parameters n and k using the determination of the dielectric constant ε (ω, T). Knowing that the semiconductor-metal transition temperature of VO2 is 68 °C, the thickness effect on the optical properties of VO2 thin films has been studied by transmittance simulations. Our results revealed a significant changes in optical properties of VO2 thin layers, which produces many interesting applications especially for smart windows.