Abstract: A spherical shock wave, generated by an underwater spark discharge in the first focus f of an ellipsoid, is focused after reflection from an elliptical surface in the second focus with peak pressures of about 100×10Pa. In this paper the influnce on the focusing effect, bust form, focal "spot" is analysed asa function of different form scale and materials of the reflector. For the quantitative research on converging Underwater shock wave, special shock wave pressure probes have been designed. By using these probes shock pressure measurements were made for ESWL unit of many manufactures. The result of measurements are excellent.