Abstract: Ultasound(US) was used to degrade nonylphenol ethoxylate(NP₁₀EO) in water in the presence of TiO₂ catalyst and H₂O₂. The effect of TiO₂ concentration, H₂O₂ concentration, ultrasound power, initial concentration and pH of NP₁₀EO on the degradation efficiency of NP₁₀EO were investigated, and the synergistic efficiency among TiO₂, H₂O₂ and US was discussed. The results show that the degradation efficieney of NP₁₀EO increases with increasing ultrasound power and TiO₂ concentration whithin certain ranges, and then becomes stable. The degradation efficiency of NP₁₀EO first increases with the H₂O₂ concentration to reach a maximum and then decreases. When pH is less than 5, the degradation effciency is high, and the degradation effciency decreases with increasing pH. When pH is greater than 5, the degradation efficiency is low. The synergistic effect on degradating NP₁₀EO in water by TiO₂/H₂O₂/US was evident, and more than 98% NP₁₀EO can be degraded in the presence of catalyst TiO₂ at a concentration of 0.4 g/L, an H₂O₂ concentration of 0.2 g/L, an ultrasound power of 600 W, an initial concentration 80 mg/L and pH=1 of NP₁₀EO within 120 min.