Abstract: The effect of ultrasonic technique degrading microcystins in different conditions was discussed. The results show that when the concentration of microcystins solution is 12.43 μg/L, the microcystins removal rate can reach 81% under 1 200 W ultrasonic treatment for 5 minutes; when the same microcystins solution is under 1 200 W ultrasonic treatment for 15 minutes, microcystins removal rate can reach 99%, nearly all the microcystins being removed. When the wastewater containing microcystis is treated by either simple ultrasonic method or ultrasonic-coagulation method, the microcystins will not increase in water. The ultrasonic method in dealing with wastewater containing microcystis has three functions at the same time: destroying the cytoderm and killing microcystis directly, inhibiting the growth activity of surviving microcystis and degrading microcystins.