Abstract: The Nantong-Luzhi section of China-Russia Eastern Gas Pipeline Project was characterized by a dense water network, high water table and poor foundation bearing capacity. To ensure construction quality and progress of the project, fully automatic welding process of copper liner external root welding that has been applied in the plain area was introduced, and verification study of welding applicability of X80M pipe steel with specification φ1 422 mm×32.1 mm was carried out in water network area. Influence of climate and geology of construction site on construction was analyzed, time of a single weld spent on each process was counted, the daily maximum efficiency of assembly line operation was calculated, and quality and performance of weld was tested. The results showed that fully automatic welding process of copper liner external root welding was carried out under conditions of climate and geology in water network area. Through reasonable deployment of personnel and equipment, precipitation, high temperature, foundation subsidence and other adverse factors could be overcome, and indicators of weld met the acceptance criteria. 10-hour maximum daily work efficiency under reasonable configuration of unit could reach 28 passes per day. The complete set of technology could finish high-quality and high-efficiency pipeline welding work in water network area.Highlights: The adaptability of automatic welding process of copper liner external root welding in water network area to unfavorable factors such as precipitation, high temperature and foundation subsidence was studied. The fully automatic welding process of copper liner external root welding was realized for high-quality and high-efficiency pipeline welding in water network area.