Abstract: Thin pressing part has high initial stress level, which affects not only the welding deformation but also hot cracking sensibility.In this paper, initial residual stress of stainless steel pressing part, a CO₂ tank, is measured experimentally.Then it is applied to the welding joint as initial stress in FEM simulation.With re-developed programs, welding process is simulated and analyzed by using thermal elastic-plastic finite element method in software MSC.Marc.The results show that strain in weld zone, radial and circumferencial strain in HAZ have few changes by implementing initial axial stress, while total strain and plastic strain in HAZ increase remarkably.Maximum total stress in the condition with initial stress is more than twice the one without initial stress.So initial axial stress is the main reason of elevated strain level of welding joints, thus increase the hot cracking sensibility.