This automatic tank girth welding machine hard surface guide rail can withstand huge pressure. The guide rail surface does not deform, making the boom move smoothly. The swing speed and swing range of the welding oscillator can be adjusted to meet the requirements of different weld widths and swing speeds. In addition, the electrical control system of this automatic tank girth welding machine adopts IP65 protection level, which is dustproof and heavy rainproof, and can be operated by remote wired/wireless control box.