Using Taguchi method to optimize the critical parameters of laser peening (LP) is presented firstly. The objective of the study is to assess the impact of laser parameters on the laser peen strengthening for the 6061-T6 aluminum alloy and optimize the process parameters to achieve higher surface residual compressive stress. In order to reduce the process cost and time, the finite element method was applied to simulate the LP process. The Taguchi method is used to formulate the experimental layout and establish the order of predominance among the identified critical parameters, and predict the optimal setting for each process parameter. The results show that three parameters related to the magnitude of compressive residual stress imply different effects. Laser shot diameter ranks first, followed by pulse width and laser power in terms of their effects on the magnitude of compressive residual stress. The best combination of levels is given by the levels (3, 3, 2). The optimal result was confirmed with a superior ultimate surface residual compressive stress of 125MP.