Dioctylphthalate (DOP) was used as the surface modifier to modify the surface of Sb2O3 nanoparticles by mechanical ball milling in this paper. The surface properties of Sb2O3 nanoparticles were characterized by XRD, Fourier transform infrared spectroscopy (FT-IR), surface contact angle measuring instrument, Zeta potentiometer and transmission electron microscope (TEM). The surface structure of Sb2O3 nanoparticles and the adsorption mode of DOP were studied, and the effects of different mass fraction of DOP on the dispersion and stability of Sb2O3 nanoparticles were analyzed. The results show that DOP can successfully coat on the surface of Sb2O3 nanoparticle by using mechanochemical method and significantly improve the dispersion of the modified Sb2O3 nanoparticles. With increasing of the mass fraction of DOP, the dispersion of Sb2O3 nanoparticles was gradually improved. When the mass fraction of DOP was 7 wt%, the average particle size of Sb2O3 nanoparticles was the smallest, and was 48 nm. However, with the increase of the mass fraction of DOP, the absolute Zeta potential of Sb2O3 nanoparticles gradually decreased and then tended to be stable finally.