Abstract: CeO₂/ZnO composite photocatalysts were prepared via in-situ precipitation of CeO₂ nanoparticles on ZnO substrate by ultrasonic microwave method and were characterized by XRD, SEM, TEM, PL, UV-Vis DRS and other techniques. The photocatalytic properties of the samples were investigated by degrading acid fuchsin (AF). The results show that ZnO has flower-shaped spherical structure assembled by ZnO nanoflskes, and its surfaces are evenly attached with CeO₂ nanoparticles. CeO₂/ZnO composite photocatalyst showed good photocatalytic activity with visible light irradiation. When the molar ratio of ZnO and CeO₂ was 20∶1, the photodegradation rate of AF reached 96.44% after 90 min of illumination, which was significantly higher than those of pure phase ZnO and CeO₂. CeO₂/ZnO indicated high stability, as the degradation rate retained 93.53% after repeated use of the same photocatalyst for 6 times. The photdegradation mechanism study shows that superoxide radical (·O₂⁻) was the main active substance in photdegrading AF.