Abstract: Bi₂O₃ nanoparticles were prepared by the microemuls ion chemical method. The structureand properties of the as-prepared Bi₂O₃ nanoparticle s were studied by means of XRD， BET， XPS and UV-vis absorption spectrum. The photocatalytic oxidation reactions of benzene， toluene and xylene were used as model reaction to measure the phot ocatalytic activity of Bi₂O₃ nanoparticles, respectively. The results show that the pr epared crystals had a tetragonal structure. The size of Bi₂O_{3 nanoparticles was 25.6～35.1　nm. The structure of Bi2O3 nanoparticles changes as the calcining temperature increases, and the electron conbining energy of the Bi2O3 surface increas es accordingly, at the same time, the photocatalytic activity for pollutants degradation is increased. The order of the degradation rates of aromatic hydrocar- bons is xylene>toluene>benzene．}

Key words: microemulsion method, Bi₂O₃ nanoparticle, charac terization, photocatalytic degradation