The invention relates to the field of nanomaterial synthesis, and discloses a preparation method for ultrafine high-purity antimony-doped tin oxide nanopowder, which comprises the following steps: taking tin particles or tin-containing compounds, antimony-containing compounds, adding strong acid, and then adding oxidizing agent and deionization Water or ultrapure water is then transferred to a closed reaction kettle, reacted at 120°C-200°C for 1-24h, cooled to room temperature, centrifuged and washed until neutral, dried, and ground to obtain antimony-doped tin dioxide nanoparticle powder. No anion impurity is introduced in the preparation process of the present invention, which ensures high purity of the prepared nanoparticles. The invention is easy to dope accurately and according to the amount, and solves the technical problems in the prior art that the doping is uneven, the particles contain anion impurities, and the particles are easy to agglomerate; the nano particles synthesized by the invention have high purity, small particle size and are easy to disperse. The coated glass prepared by the nano particles of the invention has high visible light transmittance, has the function of blocking infrared rays, and has low resistance, and can be applied to low-radiation glass and transparent conductive glass.