Abstract: Ultrasonic disintegration of waste activated sludge is a new technology to accelerate anaerobic digestion of waste activated sludge. Ultrasonic power affects the disintegration degree of waste activated sludge and energy consumption directly. To optimize the action of ultrasonic power，multi-power experiments of ultrasonic horn and ultrasonic bath reactors were carried out. It was concluded that the mode of low power with long treatment time favored waste activated sludge disintegration. However，its reaction speed was too low. Low power combination could accelerate the reaction speed. Low power combination in triple-power mode was more favorable for waste activated sludge disintegration among the combinations tested.