A three-dimensional thermal-mechanical Finite Element Model (FEM) was established by the ANSYS code to reveal the influence of fixture restraint distance on Pulsed Laser Welding (PLW) distortion of Hastelloy C-276 thin sheet with a thickness of 05 mm. The influence laws of the restraint distance on welding longitudinal deflection and transverse shrinkage distortion were investigated by using the displacement restriction assumption instead of the actual restraint condition. Experiments were carried out to measure the welding thermal cycle curves and residual distortions. The simulation results are in good agreement with that of the corresponding experiment, which validates the reliability of the FEM. It shows that the welding longitudinal deflection and transverse shrinkage distortion increase linearly with the restraint distance increasing from 8 mm to 20 mm, especially the welding transverse shrinkage distortion increases by nearly 3.6 times. Furthermore, the welding residual distortions can be controlled by reducing the restraint distance. Results dennonstrate that the FEM can simulate accurately the temperature field and the residual distortion of PLW and can provide theoretical and experimental basis for suppression of the welding distortion of thin sheets.