Abstract: The characteristics of narrow gap pulse TIG single-pass one layer welding by tungsten vibration was described in this paper. The 508-III steel for nuclear power equipment was used in the welding experiment, the appropriate form and size of narrow gap groove was designed, the factors (including welding current, arc voltage, welding speed, wire feed speed, vibration angle, the type of hot wire current, shielding gas flow) which affected the weld quality was analyzed, and the appropriate process control measures was developed. The inspection qualified weld was obtained, and the results showed that the mechanical properties meet the design requirements of China third generation nuclear power products.