In hydraulic pumped storage turbine runners, accidents due to cyclic loading often occur, that caused by residual stress at time of welding repair of a cavitation eroded part. In this study, for the aim of more fatigue property improvement of the welding materials JIS YS410,YS309, and bending fatigue tests were carried out , clarify fatigue properties and fracture mechanism of welding materials applied Ultrasonic Shot Peening (USP) treatment. The test result are summarized as follows: (1)The S-N curves of material YS410 used in this study have wide scatter since fatigue crack initiation is welding defect of mostly blowhole, on the other hand material YS309 have narrow scatter. (2)The bending fatigue limit at 10⁷ cycles with ultrasonic shot peening materials improved by 10%(YS410),25%(YS309) in comparison with untreated material. The fatigue life of USP treated welding materials has longer 10 times than un USP treatment material. The high stress amplitude below bending fatigue limit at 10⁷ cycles even if that repeats , he compression residual stress does not release. (3) It is possible to evaluate the fatigue life of welding materials by using the defect size √area and the initial stress intensity factor range calculated by defect size. The value of the threshold stress intensity factor range ΔK_i obtained in this study were 3.06 MPa·m^1/2, and ΔK_i+R considering the compressive residual stress can suppress fatigue crack growth because it is less than ΔK_i.