The invention relates to a method for adjusting a band gap of a vanadium dioxide film. The method realizes vanadium dioxide film band gap adjustment by adjustment of a band gap of vanadium dioxide for preparation of a vanadium dioxide film. The method comprises the following steps of preparation of vanadium dioxide powder having adjustable band gap: adding a specified amount of an adopted element in a vanadium dioxide powder hydrothermal method preparation so that the obtained vanadium dioxide powder having a chemical composition of V1-xMxO2 has an optical band gap continuously adjustable in a range of 0.6-4.0eV, wherein x is greater than 0 and is less than or equal to 0.5 and the adopted element M represents magnesium, aluminum, lanthanum, zirconium, gallium, niobium, tin, tantalum, manganese, nickel, chromium, zinc, titanium, tungsten, antimony, bismuth, indium or iron, and preparation of a vanadium dioxide film of which band gap is adjustable: coating a substrate with the band gap-adjustable vanadium dioxide powder dispersion liquid to obtain the band gap-adjustable vanadium dioxide film having an optical band gap continuously adjustable in a range of 0-4.0eV.