An ultrasonic stepping motor device for generating ultra-fine single droplet includes a valve housing, a valve core, and a spring. The valve core and the spring are installed inside the valve housing, and the valve core abuts against a liquid inlet of the valve housing under an elastic force of the spring. The valve housing is connected with a injector through a catheter, and the catheter is driven for linear operation by the inverse piezoelectric effect of piezoelectric ceramics through an ultrasonic linear motor. A right end of the catheter is equipped with a rubber piston, and the rubber piston is arranged in a cavity of the injector and matched with the injector. Since the piezoelectric vibrator driven catheter can produce nano feed length, and the volume of droplets overflowed each time can reach micron level, which can meet the requirements of producing micro droplets.