Three-dimensional thermodynamic analysis of simply supported high strength and low alloy (HSLA) rectangular steel plates under laser shock processing are carried out in this paper. Three-dimensional transient temperature field of the laser shock processing the rectangular HSLA steel plate is solved by the method of separation of variables. Meanwhile, the displacement and stress fields are derived by using the state-space method. It could be found that some parameters such as laser moving speed and thickness to length ratio do not affect the temperature field only, but also have great influences on the displacement and stress field. The closer the laser from the center of plate is, the greater is the revulsion amplitude of HSLA steel plate's temperature on laser area. The vibration frequency of HSLA steel plate is proportional to the increasing of laser moving speed. The thickness to length ratio affects HSLA plate's displacement and stress, but the variation law of in-plane displacement U* is not consistent with other displacement and stress components. It can be observed that applied loading form affects the deflection greatly, both on the order of magnitude and displacement shape. (C) 2014 Elsevier Ltd. All rights reserved.