Abstract: In three-phase flow, wear of Cavitations and Erosion significantly influences the behaviors of hydraulic turbine. Experimental simulation of three-phase flow wear is very difficult, but it is essential for the research on the wear of hydraulic turbine operating under severely muddy water circumstances in China. Hence, a tester was built for investigating the wear behaviors of cavitations erosion mode of steel specimens under the mixed flow of water, sand and air using an MCF-30 impact erosion-corrosion apparatus. SEM observation on the surface of test-pieces clearly showed wear trace due to cavitations erosion. Subsequent computer simulation of the conditions for cavitations and erosion under water, sand and air three-phase flow was performed so as to understand further mechanisms of cavitations erosion wear. Study indicates that a relatively more realistic simulation of cavitations and erosion requires feasible design of a tester considering some major attributions such as air as the medium in the flow, possible implosion of air bubble under high pressure, and so on. Experimental method and computer simulation of three-phase flow in this study have provided a fundamental for future research in cavitations and erosion.