The invention relates to a method for preparing diantimony trioxide nano-particles by a mechanochemical modification technology. The method comprises the following steps: (1) mixing and ball-milling micrometer diantimony trioxide, small hard alloy steel balls and distilled water to obtain nano-Sb2O3 particles; (2) washing, drying and sieving the nano-Sb2O3 particles to obtain a nano-Sb2O3 sample;(3) mixing the nano-Sb2O3 sample, small hard alloy steel balls and distilled water, adjusting the pH value, adding hexadecyltrimethylammonium bromide, carrying out ball milling, and cleaning, filtering and drying the obtained mixture to obtain cationic surfactant CTAB modified nano-Sb2O3 particles; (4) adding the cationic surfactant CTAB modified nano-Sb2O3 particles into an ethanol-water solution, and carrying out ultrasonic dispersion so as to obtain cationic surfactant CTAB modified nano-Sb2O3 particles; and (5) mixing and ball-milling the cationic surfactant CTAB modified nano-Sb2O3 particles, a silane coupling agent KH580, small hard alloy steel balls and anhydrous ethanol, and cleaning, filtering and drying the obtained mixture to obtain CTAB and KH580 compounded modified nano-Sb2O3.The method has the advantages of simple process, high yield, high operability, and easiness in realization of industrial production.