Laser shock processing (LSP) is a new and competitive technology in comparison with classical mechanical surface treatments for alloys strengthening. The compressive residual stress could be induced by LSP, which further significantly affects materials surface properties. Aluminum based alloy 6056 is used for aeronautic components and their surface strengthening is very important to increase components’ durability. The main factors of LSP, which affect the surface properties of alloys, such as surface roughness and residual stress gradient, are studied and analyzed in present study. The sin2* method with pseudo-grazing incidence X-ray diffraction (GIXRD) is used to determine the residual stress gradient after LSP treatment. In addition, the FEM simulation of residual stress distribution induced by LSP is also carried out and the results are compared with experimental data.