The invention relates to a method for preparing a titanium dioxide three-dimensional ordered nano structure, which comprises the following steps of: firstly dissolving a titanium compound into a nonpolar solvent, adding hydrochloric acid, and stirring to obtain a mixed solution; synthesizing the mixed solution into titanium dioxide powder in a reaction kettle by a solvothermal method; and then washing the powder with ethanol, and drying. The invention has simple preparation process, and a template, a surfactant or other additives do not need to be added. The prepared titanium dioxide has a dandelion-shaped three-dimensional structure formed by arranging nano rods in order and has uniform size distribution.