The surface of nano-Sb2O3 particles was modified with polyethylene glycol (PEG) using the mechanochemical method, and the dispersion mechanism of modified nano-Sb2O3 particles was also discussed. The modified nano-Sb2O3 particles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA) and UV absorbance. The results showed that the surface of nano-Sb2O3 particles was successfully coated by PEG molecules through the effect of hydrogen bonding, and the dispersion of nano-Sb2O3 particles in ethyl alcohol (C2H5OH) was significantly improved. Due to the different adsorption conformations of PEG molecules, the dispersion stability of nano-Sb2O3 particles was gradually improved with the increase of PEG average molecular weight and concentration. However, the superfluous PEG molecules would weaken the dispersion stability of nano-Sb2O3 particles.