Abstract: On basis of subsection welding' s reasonable section length attained by plane plate experiment, regulating and controlling on some hydroelectric station runner welding residual stress field is researched by means of subsection welding.The result shows for the plane plate whose dimension is 500 mm ×500 mm ×16 mm, the latter welding part can decrease welding residual stress of the prior welding part and the decreasing effect is obvious when the distance is less than 50 mm away form the end of latter welding part;subsection welding can effectively decrease welding tensile stress and then engenders residual transverse stress in the blade dangerous area. Moreover, when the welding section length of balde outlet is from 40 mm to 90 mm, the decreasing effect of residual stress is reducing with the welding section length' s increasing of blade outlet.