Abstract: In order to prevent leakage of radioactive material from the primary circuit due to the damage of heat transfer tubes, an automatic welding technology for repairing these tubes in steam generator is proposed in this paper. Using the “self-melting ring” structure and the segmented welding approach, a set of automatic welding process parameters are obtained by optimizing the welding parameters and the heat input. Through this process, the welds of the tubes have good root fusion, surface forming and mechanical properties.