Abstract: Influence of local peening on welding residual stress of Francis turbine runner is studied by means of simulation and then the experiment of welding residual stress of some hydropower station' s runner is researched.The results show that the maximum value of welding residual stress near runner' s blade outlet appears near weld bond line under the conventional welding and the local peening technology can decrease the welding residual tensile stress in the peening region.The peening effect is very obvious under the condition of plastic temperature in the peening region and the effect is obsolete under the low temperature.