The utility model relates to a special tool for fastening a butterfly valve element, and belongs to the technical field of tools for fastening butterfly valve elements of transformers. According to the technical scheme, the special tool comprises a right clamping plate (1), a tool body (2), spanner mouths (3), a first assistance hole (4) and a left clamping plate (5). The right clamping plate (1) and the left clamping plate (5) are arranged at one end of the tool body (2) symmetrically, and the right clamping plate (1), the left clamping plate (5) and the end face of the tool body (2) form a U-shaped clamping groove. The first assistance hole (4) is formed in the other end of the tool body (2) and close to the end portion, the first assistance hole (4) penetrates through the tool body (2) which is provided with the spanner mouths (3), the spanner mouths (3) are close to the first assistance hole (4), and the spanner mouths (3) are two symmetric grooves in the tool body (2). The special tool for fastening the butterfly valve element has the advantages that the structure is simple, using is convenient, an annular hoop is prevented from loosening, and leakage of the butterfly valve element is avoided.