Laser shock peening (LSP) is a surface treatment process that is performed to improve the fatigue life of components. In this process by applying a pulse of laser energy and shock wave propagation in the component, a compressive residual stress field in the metal piece is created. The main task of LSP is creating compressive residual stress and strain due to surface hardening that can improve the mechanical properties such as resistance to fatigue and corrosion of the metal parts. Residual stress distribution in the piece depends on the production and propagation of the shock wave and its interaction with the part. LSP process parameters include the magnitude of the maximum plasma pressure caused by the laser pulse, laser pulse width, number of impact at each point, and the overlap of different shots. This is important to note that improper combination of these parameters may lead to substantial tensile residual stress that is detrimental to the mechanical performance of the component. In this study, it was tried to determine an appropriate combination of these parameters by using finite element simulation of residual stress caused by LSP and validating with experimental results performed in other studies. First, through a three-dimensional finite element model, the magnitude and depth of residual stress obtained from the simulation were compared with experimental results and the model was validated. Then, using an axisymmetric finite element model, the residual stresses induced by a circular laser pulse in different states of the mentioned parameters were simulated. The effect of each process parameters on the properties of the residual stress field was studied carefully by applying a design of experiment method. These properties included maximum compressive residual stress and its depth, depth of compressive residual stress field, maximum compressive residual stress on the surface, amount of residual stress in the center of collision area, the maximum tensile stress and its depth. The results showed that the laser pulse width had opposite effects on the maximum compressive residual stress and the depth of compressive residual stress fields in which are the two important characteristics of LSP treatment. Although an increase in the laser pulse width led to a reduction in compressive residual stress, its depth increased with laser pulse width increasing. The optimal results for LSP of titanium alloy Ti-6Al-4V occurred with selection of maximum pressure between 5.6 GPa to 7 GPa and laser pulse width between 5 ns to 10 ns. Increasing the number of shots at each location also could enhance the depth of the residual stress. In addition, the effect of the overlap of spots, including the overlap percentages of 30%, 50% and 70% was investigated. The results showed that by increasing the beam overlap the compressive residual stresses was increased and residual stresses on the surface were more uniform. Studying the effects of different patterns of linear, spiral inward, and spiral outward showed that the spiral inward pattern created the most magnitude of compressive residual stress, while the pattern of treatment had no effect on the depth of compressive residual stress. Keywords: Laser shock peening, compressive residual stress, shock waves, FEM, Ti-6Al-4V