The paper focuses on the influencing parameters to the plastically affected depth and maximum residual stress in the metallic target after laser shock processing. Firstly, the dimensional analysis method is employed to find the controlling parameters, and the relationships of plastically affected depth, maximum residual stress versus peak pressure, pressure duration and laser spot size are given. Secondly, a two-dimensional axisymmetric finite element model based on LS-DYNA package is built, and the dynamic responses of metallic target subject to laser shock processing are computed with different input parameters. The result shows that the plastically affected depth is proportional to pressure duration, and the maximum residual stress is independent with it, but both of them are not affected by laser spot size within a certain range,while they have approximate linear relationship with peak pressure after reaching to a certain level.