The invention provides a method for controlling particle size and shape of nano powder, relating to a method for preparing nano powder. The method is used for preparing a nano material with spherical apparent shape and nano dimension. By using a non-polar solvent as an organic phase and a surfactant as a solidifier, self-assembly is used for solidification to control the preparation of the specific-size nano powder with spherical apparent shape. The type, consumption, stirring and other conditions of the solidifier surfactant are changed to control the particle size; and the organic solvent can be recovered and reutilized, thereby being beneficial to the environment. The prepared nano powder has spherical apparent shape and nano dimension, and has the advantages of narrow particle size distribution, uniform particle size and uniform distribution.