The nanometer anatase titanium dioxide (TiO2) (a kind of crystal type of TiO2) powder was adopted as the sonocatalyst for the damage of bovine serum albumin (BSA) used as a model protein by low-power ultrasound (US) (80 kHz, 80 W). The effects of several factors on the damage of BSA molecule were reviewed by means of ultraviolet destruction and circular dichroism spectra. It was found that the BSA molecule underwent destruction of the secondary structure and loss of the alpha-helical configuration to a certain extent under ultrasonic irradiation in the presence of nanometer anatase TiO2 powder and that the damage caused by US integrated with TiO2 was more serious than those by only US or only TiO2. Furthermore, the damage degree was aggravated with the increase of TiO2, added to saturation, and then it was slowly weakened with the excessive TiO2. When a suitable amount of acid or base was added into the BSA solution, the sonocatalytic damage was also aggravated. Because the functions of proteins are decided by their space configurations, the changes of the configurations might cause the forfeiture of their function, even the apoptosis or necrosis of cells. Perhaps, an effective method of killing cancer cells by sonocatalytic damage of protein molecules in the presence of nanometer anatase TiO2 could be obtained from these experimental results.