Abstract: The welding wire with different sulfur and phosphorus content was selected, and the flat steel without groove and K-groove welding process was used to automatic weld T91 steel high temperature superheat scree, and the welding joint quality was analyzed. The results show that the best automatic welding process of T91 steel high temperature superheat screen was to select the welding wire with low sulfur and phosphorus content and adopt the welding process of flat steel with K-groove. Compared with the wire with high sulfur and phosphorus content, the sensitivity of crystallization liquefaction crack of T91 steel superheat selected the wire with low sulfur and phosphorus content was significantly reduced. Compared with the flat steel without groove welding, the flat steel K-groove welding technology was adopted, the root of weld was not easy to crack.