Abstract: The temperature and stress fields of a ring structure laser welding are simulated by finite element method (FEM).A axial symmetry model and a thermal-mechanical coupled FEM are adopted,and it is assumed that the energy distribution of the laser beam is Gaussian distribution on the weld pool surface.The results show that the fusion zone (FZ) profile by FEM is much similar as that by metallurgic analysis.The brazing residual stresses are rather large within 2.5 mm from the brazing seam,which results in plastic deformation.The circumferential stress is larger than the axial stress,thus the axial cracking is easily occurred in beryllium ring.Radial shrinkage in beryllium ring is the same far from the brazing seam,but within 1 mm from the brazing seam,outer surface is outward expand and inner surface is inward shrinkage.The welding residual stresses exist mainly within 15 mm from the brazing seam.