Abstract: A 20 kHz and 25 kHz ultrasonic device has been developed and used to study the effect of dual-frequency ultrasound on sludge disintegration by changing COD,NH3-N,TP in filtrate.Effect factors including different frequency combination,different function mode,different power combination and different time combination of dual-frequency ultrasound have been discussed in detail.It has been indicated that dual-frequency ultrasound is more efficient to sludge disintegration.This study provide a basis for the application and the further study of sludge disintegration methods.