In order to solve the problems of heavy workload, poor stability of welding quality and high labor intensity when using traditional technology to weld the runner body overflow surface of large hydraulic turbine, a new arc additive manufacturing process is developed based on the characteristics and difficulties of arc additive technology. The results show that this technology is effective and feasible,ensures the consistency of additive size of overflow surface,realizes stable and efficient welding quality, reduces labor intensity of workers, and achieves the effect of cost decreasing and benefit increasing.