Abstract: In medical ultrasound imaging and therapy, internal tissues, blood vessels, bones, and other structures can cause severe waveform distortion, adversely affecting ultrasound focusing performance. This paper discusses the generation of non-diffracting ultrasonic focused beams. By designing a metalens based on Airy beam, the high-efficiency focusing of underwater ultrasonic beam is achieved. Through simulation and experimental measurements, the focusing performance of the designed metalens is confirmed to be unaffected by the presence of obstacles, offering new methods for ultrasound imaging and therapy in scenarios such as transcranial and intercostal applications.