The cavitation erosion resistance ofl 6Cr5Ni martensitic stainless steel used in hydro turbine components has been studied in a vibratory cavitation test rig as perASTM G32 standard Three stages of rate of mass loss, surface roughness and the retained austenite content with cavitation time has been studied. Quantitative 3D surface roughness parameters such as average deviation (Ra), standard deviation ( Rq), mean roughness depth(Rz) and change in surface volume with cavitation time has been studied using confocai laser scanning microscope with a view to identify the damage mechanisms in these steels. The correlation between roughness profde parameters and the transition between the incubation and acceleration stage was established The present study indicates that the 3D surface parameters can become a useful tool to monitor the progress in cavitation damage.