Ultrasonic airlift loop reactor (UALR) shows potential and wide application for wastewater treatment. In this paper the performance and efficiency of UALR in dimethoate degradation were presented. The effects of O-3 flow rate, ultrasonic intensity and initial concentration of dimethoate on degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O-3 transfer rate. The results showed that UALR not only increased degradation rate, but also was better than the simple sum of degradation by O-3 and ultrasound separately. Under the operation conditions of O-3 flow of 0.34 m(3).h(-1), ultrasonic intensity 3.71 W.cm(-2), and initial concentration of dimethoate at 20 mg.L-1, the degradation rate of dimethoate increased to 80%. UALR seems an advisable choice for treating organic wastewater and this process may have wide application prospect in industry.