The influence of flow velocity and cavitation number on erosion rate was studied by using the cavitating liquid jet method. The optimum stand-off distance was established at four cavitation numbers, and the distance coincides with that given in the ASTM G 134 standard. The cavitation erosion tests were carried out at a constant cavitation number at various flow velocities. The maximum mean depth erosion rate (MDERmax) increases with the flow velocity with the power of 3.9 to 4.6 and the power does not change with cavitation number. The MDERmax increases with cavitation number between 0.015 and 0.03. A linear relationship was obtained between MDERmax and ∑F²_i (summation of squares of impact loads which is equivalent to the impact energy) under various cavitation.