For most uncomplicated urinary tract stones, extracorporeal shock wave lithotripsy is the first choice. In China, extracorporeal lithotripsy is relatively inexpensive and therefore widely used for outpatient treatment of urinary tract stones. The most used machine in the world is the HM3 lithotripter from Dornier, Germany, which uses high voltage and large capacitance to form a high voltage circuit to generate shock waves through electrode discharge, which is focused by the reflection of elliptical reflector, and the energy accumulation is enhanced to a certain value to achieve stone crushing effect. In addition to electrohydraulic lithotripters, there are also electromagnetic and piezoelectric crystal lithotripters with similar lithotripsy principles. The transmission characteristics of shock wave is close to sound waves, acoustic impedance in different media have great differences, water and human body acoustic impedance close, shock wave into the body almost no reflection, less energy loss, almost no damage to soft tissue. At present, the water capsule is also used as the transmission medium of shock wave into the body. The acoustic impedance of urinary tract stones is about 5 to 10 times that of water, and due to the difference in impedance, compressive stress is generated to break up the stones. The greater the difference in acoustic impedance between the two media, the greater the compressive stress, and the easier it is for the stone or tissue structure to be destroyed. The compressive stress on the surface of the stone causes the stone to break up, while the cavitation produces a jet of water that causes the stone to flake off the inner surface of the fissure, and the continuous shock wave causes the stone to break up layer by layer and finally crush completely and discharge from the body. Therefore, extracorporeal lithotripsy is safe and effective, and is clinically applicable to most urinary tract stones.