Abstract: Based on the characteristics of a mixed flow power plant with a large number of long and short blade form runners, narrow working space between blades, and high mechanical performance requirements for welds, the problem of narrow operating space between blades is solved by using separate assembly and welding of long blades and horizontal assembly and welding of short blades through shafts. The welding quality and mechanical properties of welds are ensured by adjusting the welding material and welding process.