Cavitation-erosion is a hydrodynamic phenomenon that results in the formation and collapse of vapor bubbles in a liquid. Cavitation damage is encountered in a wide variety of fluid handling machinery and over a broad range of liquid pressures and temperatures. In this study, cavitation damage was investigated by using the piezoelectric vibrator with 20kHz, 50μm to cavity generation apparatus. At the first cavitation test, coated composite material specimens appear to generating the low bubbles due to damping vibration. This study is mainly compared with cavitation test (ASTM G 32) and modified cavitation test. And it is also concerned with phenomenon of cavitation-erosion on the several materials. In order to compare the both test methods, cavitaion weight loss and rate of the several materials in fresh-water and sea-water measured and observed with digital camera.