Extracorporeal shockwave lithotripsy（ESWL） is a non-invasive method for the treatment of urinary calculi

with more than 95% success rate in clinic. The shock wave energy is a key factor in the success of this method. Therefore

it is introduced the forming

propagation and focusing of shockwave

electric field energy of shockwave generator

and lithotripsy principle. Then the optimal energy of the shockwave is analyzed from the success rate density distribution of ESWL. The subjects wear patients aged 18

8

3 with ureteral stone in

the radiographic imaging characteristics in left or/and right and complete data of ESWL from outpatient. And they have been treated successful by ESWL. The mathematical expectation and variance are got by ESWL success rate density distribution function

and obtain the best energy range of ESWL. The results show the mathematical expectation is 535 m J/mm

2

and the mean variance is 157 m J/mm

2

from 5 747 cases. The optimum energy is 418

7

32 m J/mm

2

. However

the energy is determined by the focus energy level. Generally

Ⅰ level of the focus energy was about 10 m J/mm

2

Ⅱ level 20

4

0 m J/mm

2

Ⅲ level 30

3

00 m J/mm

2

Ⅳlevel 400

1

200 m J/mm

2

. The energy level can choose according to the size and density of the stones. This conclusion helps clinicians to select the energy of ESWL based on the actual stone for obtain the best ESWL successful.