Laser peening is a novel surface strengthening technique used to improve mechanical property of materials by utilizing mechanical effect produced by laser induced plasma shock wave. However, during the process of laser peening, effects of high pressure shock wave may cause macroscopical deformation of thin-walled workpieces and result in failure of parts. The work aims to clarify the characteristics of mechanical deformation characteristics of plate subject to laser shock in order to control macroscopical deformation process of plate subject to laser shock. Based on theoretical analysis of deformation process of cantilever slab under laser shock loading, a model of strained deformation of cantilever plate under laser shock was constituted and the deformation formula of plate under laser effects was calculated by theoretical derivation. The relationship between the plate deformation and various parameters such as laser energy, plate thickness was also studied. Accuracy of the theoretical formula was verified by combining single-point & multipoint lap shock experiments and finite element analysis. Experimental results showed that theoretical value, experiment value and finite element analysis results acquired by established theoretical calculation of plate were similar. The plate deformation was sensitive to variation in thickness. Under given conditions, minor plate deformation and even no obvious deformation appeared when the thickness exceeded 3 mm. Plate deformation increases with the increase of laser energy and spot number. Plate thickness has great influence on deformation and shall be considered when designing laser peening parameters.