A test for decomposing low concentration Dimethoate in simulated wastewater by ultrasonic wave was introduced.The effect of irradiation time,dosages of H 2O 2,initial concentration of Dimethoate and temperature on decomposition were explored.The results show that the longer irradiation time is,H 2O 2;in the lower concentration range of Dimethoate solution,the degradation efficiency is enhancing with the increase of concentration;and the suitable temperature for degradation is under 30℃.