Abstract: Briefed in the essay are the pre-welding and finish welding processes for SAWH pipe and characteristics thereof.Described are the common defects of the pipe as occurring in the pre-welding process,such as porosity,entrapped-slag,burn-through,weld displacement,weld misalignment,and excessive formation weld gap,straightness and ovality,etc.Analyzed is the influence by the in-pre-welding defects on the quality of finish welding.Based on the identified elements responsible for the pre-welding quality,control measures for improving the pre-welding quality are proposed,and taken.Thanks to the measures,the pre-welding quality of the SAWH pipe is tremendously improved to well meet the requirement for finish weld process operation.