Finite element method (FEM) simulation of laser shock processing (LSP) is an effective method to predict the residual stress field and optimize the laser shock parameters. The FEM is applied to attain the numerical simulation of residual stress field of material treated by laser shock processing. The history of energies during explicit dynamic analysis is discussed and is well correlated with the result derived by shock wave theory. The method of solution time choosing for explicit analysis is presented based on the history of energies. Residual stress distribution of single and multiple laser shock is analyzed and validated by experimental result. The analysis results indicate that compressive residual stress of material is uniform on surface and the stress gradient in depth is small. Compressive residual stresses and plastically affected depth are extensively increased and gradually reach the saturated state by multiple laser shock.