The invention discloses a preparation method of a shape-controllable WO3 thin film. The preparation method lies in that firstly, sodium tungstate, hydrochloric acid and hydrogen peroxide are taken as the raw materials, a seed layer is pre-deposited on FTO conducting glass by the sol-gel method, and finally tungstic acid, sodium tungstate, hydrogen peroxide and hydrochloric acid are taken as the raw materials for preparing the WO3 thin film by utilizing the hydrothermal method. According to the preparation method of the shape-controlled WO3 thin film, both the synthetic process and the needed production equipment are simple, industrial production is easy to realize, and the WO3 thin film of which the shape can be effectively controlled is obtained by changing the solvents ratio.