Shell Process gasifier with waste boiler has the advantages of wide adaptability of energy coal type,high carbon conversion rate,large single-series production capacity,long operation cycle,etc. But the manufacturing technology is monopolized by foreign countries,and there is no manufacturing experience in China. This paper points out the process method of automatic welding of non-linear thick wall large diameter cylinder butt joint in Shell gasifier and chemical container,which has been successfully used in production practice. And from the product structure characteristics,product focus,assembly size requirements,automatic welding characteristics,how to realize automatic welding of non-linear thick-walled large-diameter cylindrical elliptical section is introduced. The process has been successfully applied in engineering practice with good results.