The invention relates to a repair welding process used after thread blind hole depth difference exceeding, and belongs to the technical field of transformer production. According to the technical scheme, as for through-top, protruding and too-thin thread blind holes, a pointed cone (4) is used for knocking through-top, protruding and too-thin parts at the back face of workpieces, the knocking force enables the parts to form conical grooves, and conical tips of the conical grooves cannot exceed conical ends of bottom holes; and the thread blind holes are filled with copper bars or asbestos cords, repair welding is carried out at the conical grooves, the repair welding thickness is slightly larger than that of the surfaces of the back faces of the workpieces, and then rubdown is carried out. The repair welding process has the beneficial effects that repairing after the bottom holes of the thread blind holes of the parts are too deep is achieved, the parts can be rapidly desterilized while the original reliable sealing thickness of the parts is recovered, the material cost and the maintaining cost for flange replacement are reduced, and the repair welding process is particularly suitable for the transformer production process.