Abstract: There is a large amount of prefabrication of process pipelines in natural gas processing factories.Fine wire submerged arc automatic welding has been employed to weld 20G and 20G(sulfur-resistant)pipelines to improve production efficiency and solve the large welding workload and tight construction period issues.The metal powder cored welding wire was used for root welding of the 20G pipeline in non-acidic medium,while solid sulfur-resistant welding wire argon arc welding(or RMD)was used for root welding of the 20G(sulfur resistant)pipeline in acidic medium.Both process pipelines are filled and covered with fine wire submerged arc welding.The welding process can cover a pipeline wall thickness range from 15mm to 30mm,and meets production needs through welding process evaluation.