To improve the surface quality and shape control level of hydraulic machining aluminum alloy, a non-contact roughness characterization method was proposed, by the 3D image processing technology. According to the damage morphology of aluminum alloy, it studied the regional failure mechanisms of aluminum alloy under hydraulic penetrating, and quantified the dynamic evolution processes in different damage regions. Then through the roughness multiple indicators, it addressed the surface roughness distribution and evolution characteristic of aluminum alloy by hydraulic penetrating. The results show that the damage morphology of aluminum alloy under hydraulic penetrating can be subdivided into the crack area, the damage deformation area and the plastic extension area. In the radial direction of the water jet, the surface roughness has three distinct change processes, including the increasing stage, decreasing stage and the stable stage, and the dispersion and volatility of the surface roughness decrease gradually. The peak roughness and the impacting time have a significant positive correlation. The concentration of the surface roughness distribution probability tends to be higher with the time.