<p>Ni-based superalloy thin plates have been extensively applied in critical aviation components, such as turbine disks and engine blades, owing to their excellent comprehensive performance over a wide temperature range. In this paper, a transient thermo-mechanical coupled finite element model was established for the laser beam welding (LBW) of GH4099 superalloy. A DFLUX user subroutine was developed to accurately simulate the nonuniform distributed heat flux as a function of position and time. The correctness of the model was verified by comparing the experimental and simulated molten pool morphologies. Then, the effects of welding power and welding speed on the temperature evolution and residual stress were systematically predicted. The microstructure and mechanical properties of welded joints were investigated using electron backscatter diffraction (EBSD) and tensile tests. Numerical simulation revealed that the residual stresses are symmetrically distributed on both sides of the weld. With increasing welding speed or decreasing welding power, the residual stresses in the weld zone decrease significantly, and concentrate at the end of the thin plate. However, the values of transverse high tensile stress in the weld unstable zone gradually increase, which results in a high risk of weld depression. In addition, the longitudinal high tensile stresses on the upper surface of the weld may cause ripple formation. Moreover, the higher welding power will lead to grain coarsening in the molten pool region, which increases the elongation of the welded joint, while reducing the yield strength and tensile strength. The research in this paper provides a basis for the rational selection of parameters for laser welding of Ni-based superalloy thin plates.</p>