The surface morphology and deformation depth of the copper targets treated by nanosecond laser shock peening (LSP) are measured by optical microscope (OM), 3D profile and so on. Non-contact optical profile is used to measure the surface roughness of the metal targets. The source of micro defects is analyzed emphatically when absorption layer is aluminum foil tape. Samples with different surface roughnesses are treated by LSP. Experimental results show that there will form macro dents and micro convex-concave structures on the impacted regions when black paint is used as the absorption layer. When the absorption layer is aluminum foil tape, besides the macro dents, there will form large amounts of micro defects on the impacted region. Through analysis and experimental research, it is confirmed that the formation of micro defects are associated with the air bubbles existed in the glue on the back of aluminum foil tape. LSP can increase the overall roughness but reduce the maximum height of roughness when the original roughness is high. When the surface smoothness is high, LSP can increase the overall roughness and the maximum height of roughness.