TiO2 nanoparticles were synthesized by the hydrolysis and condensation of TiCl4 in a mixed solvent of iso-propyl alcohol and water with or without ultrasound treatment. As-prepared powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy filtering transmission electron microscopy (EF-TEM), particle size analysis and BET surface area analysis. The specific surface area, thermal stability and crystallization of the as-prepared samples treated with ultrasound were higher than those of samples treated without ultrasound. To examine the photocatalytic activity of the as-prepared TiO2, the photodegradation of MB which is a typical dye resistant to biodegradation has been investigated on TiO2 powders in aqueous heterogeneous suspensions. The photocatalytic degradation of a aqueous solution of methylene blue shows a remarkable increase when it is carried out with ultrasound in all cases.