The Er3+:YAlO3/ZnO composite, a new photocatalyst that could effectively utilize visible light, was prepared by ultrasonic dispersion and liquids boiling method in this work. In succession, the Er3+:YAlO3/ZnO composite, Er3+:YAlO3 particle and pure ZnO powder were characterized by X-ray diffraction (XRD). The Acid Red B dye as a model compound was degraded under solar light irradiation to evaluate the photocatalytic activity of the Er3+:YAlO3/ZnO composite. In addition, the effects of Er3+:YAlO3 content, heat-treated temperature and heat-treated time on photocatalytic activity of Er3+:YAlO3/ZnO composite were reviewed through the degradation of Acid Red B dye under solar light. Otherwise, the effects of initial concentration, Er3+:YAlO3/ZnO amount, solution acidity and solar light irradiation time on the photocatalytic degradation of Acid Red B dye were investigated in detail. It was found that the photocatalytic activity of Er3+ :YAlO3/ZnO composite is much higher than that of pure ZnO powder for the similar system. Perhaps, the use of this Er3+:YAlO3/ZnO composite may provide a new way to take advantage of ZnO in sewage treatment aspects using solar energy. (C) 2008 Elsevier B.V. All rights reserved.