The tool is suitable for processing steel pipes with large inner holes. It adopts a symmetrical two-edged blade structure. The blade is fixed on the tool holder by screws, and the alloy guide pad is fixed on the support seat by screws. The tool holder and the support seat are positioned by a sizing ring, and the sizing ring cooperates with the mandrel. The mandrel fixes the tool body by screws. The outer circle size of the boring tool blade and the alloy guide pad is synchronously adjusted by the sizing ring. Different sizes can be adjusted at one time through the sizing ring, which reduces the tool adjustment link, effectively ensures the stability of the tool size, and greatly improves the efficiency. At the same time, a symmetrical two-edged blade structure is adopted to ensure the roundness of the inner hole processing, two rows of guide supports, the first row is symmetrical, and the blades in the same row are 90° apart. The second row of guide supports uses four bakelite circumferences evenly distributed to ensure the straightness and roundness of the inner hole processing. The bakelite plays an effective guiding, supporting and shock absorbing role. The efficiency is at least twice as high as that of the original old deep hole boring tool, and the straightness per meter is guaranteed to be within 0.5mm, which is at least 2 times higher than the original processing straightness.