Abstract: As an important part of the space environment simulator, the thermal shroud is used to provide low temperature and black background. The structure of a stainless steel pipe welded with copper fins is a new type of thermal shroud developed in recent years. The key issue for this kind of thermal shroud is how to weld firmly the two different metallic materials parts. The manual argon arc weld used to be the main technology in the past, but its efficiency and reliability can not meet the current requirements. So an automatic welding device is developed to weld the stainless steel pipe and copper fins. This paper discusses its design and the welding parameters.