Barrel rounding tool

The utility model discloses a barrel rounding tool which comprises middle tolerance zone circular rings, inner support rings and outer tool frames. The middle tolerance zone circular rings are used for positioning and fixing the outer-diameter side of a barrel, inner support components are uniformly distributed on the circumferences of the middle tolerance zone circular rings and are used for supporting the outer-diameter side of the barrel, the inner support rings are arranged on the inner side of the spread barrel, three separate sheets are spliced with one another to form each inner support ring, and the outer tool frames are used for constraining the outer-diameter side of the barrel, so that excessively large spread diameters, which are larger than required diameters, of the barrel can be prevented. The barrel rounding tool has the advantages that requirements can be met, and the barrel rounding tool is simple in structure, easy to manufacture and low in cost.