Abstract: According to the functional requirements, the design principle of automatic all-direction tube-sheet argon-arc welding machine was put forward in this paper. Then the key problems of this machine were described, such as reliable wire feeding, accurate positioning, flexible water and gas supplying. Finally, a tube-plate welding head with high performance was designed. This welding head with the conductive ring and static positioning, dual water and gas supply, has the advantages of compact structure, reliable operation, strong applicability etc. The production practice shows that the welding head can effectively ensure the quality of the welded joint, and significantly improves the production efficiency.