In order to degrade some pollutants effectively under ultrasonic irradiation, the Co-doped and Cr-doped mixed crystal TiO2 powders,with high sonocatalytic activity,were prepared as sonocatalyst. The Co-doped and Cr-doped mixed crystal TiO2 powders as sonocatalyst were prepared through sol-gel and heat-treated methods from tetrabutylorthotitanate, and then were characterized by XRD and TG-DTA technologies. In order to compare and evaluate the sonocatalytic activity of the Co-doped and Cr-doped mixed crystal TiO2 powders, the low power ultrasound was as an irradiation source and the azo fuchsine was chosen as a model compound to be degraded. The degradation process was investigated by UV-vis, TOC, ion chromatogram and HPLC techniques. The results indicated that the sonocatalytic activity of Cr-doped mixed crystal TiO2 powder was higher than that of Co-doped and undoped mixed crystal TiO2 powder during the sonocatalytic degradation of the azo fuchsine in aqueous solution. These results may be of great significance for driving sonocatalytic method to treat non- or low-transparent industrial wastewaters. (C) 2009 Published by Elsevier B.V.