The invention relates to a monometer material, in particular to a preparation method of tin dioxide monometer powder uniformly doped with antimony. The preparation method comprises the following steps: adding the alcoholic solution of antimony and ammonia into tin solution under the stirring process, wherein the addition is completed within 15 to 60 min and the pH value of reaction liquid is between 3 and 4; then aging the reaction liquid for 2 to 5h at the temperature of 50 to 70 DEG C, filtering and washing the reaction liquid to remove water soluble inorganic salt, dispersing an organic solvent, and drying and removing the organic solvent; and calcining for 0.5 to 3h and obtaining dark blue ATO nanometer powder. The alcoholic solution of antimonic salt and precipitator ammonia solutionare synchronously dripped into tin salt aqueous solution in a double-dripping manner; and tin and antimony are hydrolyzed synchronously under the action of a compounding agent, so that the antimony isuniformly doped. The invention overcomes the defects of uneven adulteration of the antimony and easy reunion of particles when the ATO nanometer powder is prepared by using conventional method, and enlarges the application scope of the ATO nanometer powder.