Our research which is based on the ultrasound technology discusses the mechanism concerning about the inhibition to the cyanobacteria caused by the low-intensity ultrasound.It suggests that treat for 5 min every 4~5 days is the best way under the condition.It points out that the low-intersity ultrasound destroys the structure of the PBS and interferes the composing of cholophy in solving water-bloom.As a result increasing of bimass was controlled.