Abstract: The residual stress distribution of the ERW straight welded casing was studied by using X-ray diffraction and cutting methods. It had been found that the residual stress distribution exhibited a asymmetric characteristic along the circumferential direction,and the residual stress near the welding line was very high,close to the yield strength;The residual stress of exterior surface after cutting changed from tensile stress to compressive stress with the increase of aging time,while a reverse phenomenon was observed in the interior surface.