Abstract: This paper analyses the argon arc welding techniques available for welding the outside layer of thermos bottles made of 0.3mm stainless steel,comparing their merits and demerits on the basis of their technical and economical features.Extensive technological research has been made in the design of continuous argon arc welding with tungsten electrode on a single D.C.double-position machine.A special apparatus has been developed for welding stainless steel thermos bottles,with a rate of one piece per minute.The parer offers the new idea of preventing burnthrough in welding ultra-thin stainless steel sheet by leaving an opening in assembly,which can be filled with the help of transverse shrinkage in welding.This idea has been verified in practical operatian on the selfmade double-position welding machine,which gives a rate of successful welding joints higher than 95 percent.