Abstract: By simulating the real condition of field welding of closured weld joint, the constraint stress and welding residual stress status in adopting butt joint and overlap joint were understood and grasped, so providing foundations of selecting feat closured weld joint type for pressure pipes′ welding of No.1～No.6 unit at Three Gorges Left Bank Power Station .

Key words: pressure pipe, closured weld joint, joint type, constraint stress, welding residual stress