The numerical simulations and experiments were employed to investigate the effect of boundary constraint conditions of thin plate on residual stresses and plastic deformation induced by laser shock peening. Two boundary conditions, bottom fully constrained and both ends clamped, were used to compare residual stresses distribution and deformation morphology of 7075 aluminum plates after impacted by multiple laser shock peening. The results show that micro-dents were generated in impacted regions of both cases after treated by laser shock peening. The plate still kept flat without cross-sectional deformation when its bottom surface was fully constrained, while the overall upward convex deformation was produced in the impacted region of plate with both ends clamped. Moreover, the maximum compressive residual stresses existed on the surface of both cases, which was 299.0 MPa in the plate with bottom fully constrained and 251.6 MPa in the other case. Different styles of residual stresses field are also found in the thickness direction. The residual stresses from the impacted surface to the bottom was "compressive residual stresses -tensile residual stresses" in the plate with bottom fully constrained, while it was "compressive residual stresses-tensile residual stresses-compressive residual stresses" in the plate with both ends clamped.