The work aims to explore the impingement and cavitation erosion effects of submerged water jet on aluminium alloy and Cu alloy. Effects of jet pressure, impingement duration and target distance were studied to obtain the effects of key jet duty parameters on jet impingement and erosion. Residual stress on the material surface was measuremd and analyzed at low pressure and surface morphology of the material surface was observed at high pressure. Residual stress increased as the jet pressure increased, it was up to 91 MPa when the impingement duration was 20 minutes and jet pressure was 40 MPa. At the initial stage of cavitation erosion, dispersely distributed cavitation erosion pits were present on specimen surface, reflecting the effects of cavitation bubbles. With the enhancement of cavitation erosion effects, cavitation erosion pits on specimen surface expanded and plastic deformation was present simultaneously. It achieved the most significant impact when the impingement pressure was 300 MPa, target distance was 7 cm and impact duration was 15 minutes. The submerged water jet can strengthen the metal surface at low pressure and cause the metal surface to produce the pits and plastic deformation at high pressure. Surface morphology characteristic reflects the dominant effect of dispersed bubbles produced as a result of cavitation. Though the submerged water jet presents continuous jet velocity distribution, the damage on the specimen surface largely depends on cavitation phenomenon.