Vibratory cavitation formation and collapse and consequent material damage are controlled mainly by the driving pressure amplitude. This amplitude is the sum of the generated pressure wave amplitude and the reflected pressure wave amplitude from cylinder block surface. A series of vibratory cavitation erosion tests at different water gaps were carried out at vibration frequencies ranged from 1.85 to 6.4 kHz. Also a series of tests using a rubber disc to act as an absorbing surface instead of the normal brass bottom of test liquid container were conducted. It was found that the erosion rate increases due to the proximity of a reflecting surface, and by suitable treatment of the reflecting surface, this increasing can be eliminated.