The invention discloses a preparation method of bowknot-shaped antimonous oxide. The preparation method comprises the following steps of: dissolving a raw material, i.e. a trivalent antimony salt, in an ethanol-deionized water mixing solvent according to a volume ratio of 1: 1-1: 3 to prepare 0.01-0.1mol/L of solution; adding a surfactant to the solution, adding an alkaline regulator to regulate the pH value to be 8-12, then reacting for 1-24h at 100-250 DEG C in a sealed environment and naturally cooling to the room temperature; and collecting a reaction product, alternately washing and drying the solid product through deionized water and absolute ethyl alcohol to obtain the bowknot-shaped antimonous oxide. The preparation method disclosed by the invention is simple and controllable, hasshort period and low cost and is beneficial to large-scale industrial production; and the obtained product has high purity and uniformly-distributed particle sizes and is of a bowknot shape because two ends of the particle are split.