The invention provides a method of preparing carbon-doped metal oxide nanoparticles by means of the supercritical anti-solvent technology and high-temperature calcination. The method comprises the following steps: dissolving metal nitrate and a methyl vinyl ether-maleic anhydride copolymer in a solvent to form a mixed solution; then atomizing the mixed solution placed in a columnar piston injectorat a certain flow rate and injecting the mixed solution to a supercritical fluid; preparing polymer nanospheres of inorganic salt embedded with inorganic salt under the anti-solvent action of the supercritical fluid at a temperature of 308-330K and at a pressure of 10-12MPa; and calcining the nanospheres embedded with the metal nitrate and the methyl vinyl ether-maleic anhydride copolymer at a high temperature to finally obtain the carbon-doped metal oxide nanoparticles, the grain sizes of which are 10-100nm. The synthetic method is simple and easy to control operating condition, and the function and application of the metal oxide nanoparticles are improved greatly.