The invention belongs to the technical field of preparation of strontium titanate and discloses a preparation method of nano-scale strontium titanate powder. The preparation method comprises the following steps: (1) uniformly stirring and mixing 30-40 parts of water, 5-6 parts of concentrated hydrochloric acid and 100-150 parts of absolute ethyl alcohol in parts by volume at a constant temperatureof 25-35 DEG C; (2) uniformly stirring and mixing 35-45 parts of absolute ethyl alcohol and 12-14 parts of tetrabutyl titanate in parts by volume at a constant temperature of 30-40 DEG C, adding strontium carbonate, stirring for 15-25 minutes, carrying out ultrasonic treatment for 40-60 minutes, adding the solution obtained in the step (1), and standing at the room temperature for 3-5 hours in adark environment, wherein the molar ratio of tetrabutyl titanate to strontium carbonate is (0.9-1.0) to (1.0-1.1); and (3) standing, heating and drying the product obtained in the step (2), grinding,and maintaining the temperature at 800-1100 DEG C for 2-4 hours in an air atmosphere, so as to obtain strontium titanate, wherein the volume part is counted by ml, and the mass part is counted by g. The surface of strontium titanate is coated with a titanium dioxide precursor, so that the mixing uniformity of two solid phases and the contact area between the two solid phases are increased during the sintering, and high-purity nano-scale strontium titanate powder is prepared.