The invention discloses a preparation method of vanadium dioxide nanopowder, which comprises: 1) adding tetravalent vanadium salt into deionized water, stirring until completely dissolved to obtain solution a; 2) adding a precipitating agent into solution a, Adjust the pH to 8-12, stir for a period of time to obtain a suspension b; 3) separate the suspension b to obtain a precipitate c, disperse the precipitate c in deionized water, add hydrogen peroxide, adjust the pH to 3-6, and age at room temperature 1 to 6 hours to obtain the suspension d; 4) separate the suspension d to obtain the precipitate e, dry the precipitate e for a period of time, calcinate at 450-700°C for 1-5 hours under the protection of an inert gas, and cool to room temperature Afterwards, vanadium dioxide nanopowder is obtained. The invention has reasonable and ingenious design, simple preparation process, readily available raw materials, low reaction energy consumption, less environmental pollution, short production cycle, no need for expensive production equipment, low production cost, and easy large-scale production.