The invention discloses a method for preparing micron-grade stannic oxide powder which is applicable to conductive glass, semiconductor materials, high-class ceramic colored glaze materials or electric operation. The method comprises the following steps: dropping an ammonium bicarbonate solution, an ammonium carbonate solution or a mixture solution of ammonium bicarbonate and ammonium carbonate into a reagent-grade sodium stannate solution, controlling the pH value of a reaction liquid to be within the range of 9.0-10.0 so as to prepare tin hydroxide hydrate with high-dispersity, subsequently pulping the tin hydroxide hydrate by using pure water, further conditioning the pH value of the tin hydroxide hydrate pulp so as to obtain metastannic acid, and finally putting metastannic acid solid into a high-temperature furnace to be calcined and dehydrated so as to obtain the high-purity micron-grade stannic oxide powder. According to the method disclosed by the invention, micron-grade powder can be prepared without crushing, the production process is environment-friendly, the production equipment is simple, industrialization is easy to achieve, the micron-grade stannic oxide powder product prepared by using the method disclosed by the invention is small in particle size, high in purity, single in component and capable of meeting the requirements of conductive glass, semiconductor materials, high-class ceramic colored glaze materials or electric operation.