In this work, Fe-doped mixed crystal TiO2 powder as sonocatalyst was prepared by the sol-gel method and heat treatment, and a novel method combined with ultrasonic irradiation was propounded to degrade the organic polluted water. First, the Fe-doped mixed crystal TiO2 powder was characterized by TG-DTA, XRD, and TEM techniques. Ultrasound was used as the irradiation source and the azo fuchsine was chose as the model compound. Then a series of degradation experiments was carried out in the presence of Fe-doped mixed crystal TiO2 powder. Also, the degradation process and some influencing factors, such as irradiation time, doping Fe3+ ion content, added amount of catalyst, and initial concentration of azo fuchsine solution, on the degradation were investigated by UV-vis spectra, ion chromatography, and HPLC. Through the degradation of azo fuchsine, it was found that the combination of ultrasonic irradiation and Fe-doped mixed crystal TiO2 powder can completely degrade the azo fuchsine in aqueous solution. Because of the good degradation efficiency, this method may be an advisable choice for the treatments of non- or low-transparent wastewaters in the future. (C) 2007 Elsevier Inc. All rights reserved.