The high quality vanadium dioxide (VO2) thin films have been fabricated successfully on sapphire by a simple novel sputtering oxidation coupling (SOC) method. Transmittance spectra of vanadium dioxide film have been measured between 25 °C and 90 °C. The thin film samples exhibit a good insulator-metal transition near room temperature. The optical constants of VO2 thin film samples were derived by fitting the transmittance spectra using the Drude-Lorentz model. In order to improve the transition efficiency, the thin film thickness was optimized by the optical design. The calculated results with different thin film thickness show that VO2 thin film with 84 nm owns a maximums value of the transition efficiency. This research will promote VO2 thin film optical performance improvement for the smart windows.