Abstract: The Paper goes preliminarily into the technology of rotary electrical arc welding and discusses the main technical factors like the welding current,excitation current, rotary speed and time,and gap of butt-joint,which affect the quality of the welded joints.And it gives the technical data used in the rotary arc welding of steel pipes ranging from φ76×3.5 to φ114×4mm with tested results.It can be prodicted that rotary arc welding applied to the welding of pipes of medium and small sizes would be a strongly competitive and effective method.