The invention provides an ultrasonic flushing instrument and relates to the field of oral medical instruments. The ultrasonic flushing instrument comprises a liquid storage tank, an ultrasonic generator, a first water pump, a second water pump, a recovery tank, a handle, a back suction cavity, a flushing syringe needle, a connecting pipe, a flushing head, a first supporting rod, a second supporting rod, a first switch, a second switch, a third switch and multiple infusion tubes. In the using process, the first switch is turned on, disinfectant liquid can be sprayed to root canals of the teeth of a patient, the third switch is turned on at the same time, sound waves generated by the ultrasonic generator can be used for loosening scraps and a smear layer on the root canal wall of the teeth during root canal preparation to facilitate flushing and cleaning through the disinfectant liquid, and the second switch can be turned on at the same time to suck back the disinfectant liquid in a tooth marrow cavity into the recovery tank in time. The ultrasonic flushing instrument is convenient to operate, saves time and labor, makes the time of a doctor beside a chair shorter, improves treatment quality by the doctor and economical efficiency, and relieves the pain of the patient.