Vanadium dioxide thin film undergoes an insulator-metal phase transition at about 68 ^oC, which is accompanied by an abrupt and large change of optical properties especially in the infrared region. Vanadium dioxide thin films have a potential application in smart windows due to the above unique thermochromic property. As a result, vanadium dioxide thin films have become a hot research topic in smart windows. However, several drawbacks such as small solar modulation ability, low luminous transmittance, high phase transition temperature, and undesirable thermochromic stability have hindered the practical applications of vanadium dioxide thin films in smart windows. In order to solve these issues, great efforts have been made by researchers in recent years. This review focuses on the important preparation methods (magnetron sputtering method, chemical vapour deposition method, sol-gel method, and hydrothermal method) and the strategies for improving the thermochromic properties (doping, multilayer films, and composite films). We hope that this review can provide references to the researchers who investigate the thermochromic properties of vanadium dioxide films as well as smart windows.