The utility model discloses a special dismounting tool for a transformer oil tank and belongs to a special dismounting tool for power equipment maintaining and checking. The utility model relates to a special tool for a loaded tap changer oil tank of a universal transformer, which mainly comprises a high-strength full-thread screw rod (1); a hoisting ring (2) (used for hoisting over-heavy oil tanks) is mounted on the upper part of the high-strength full-thread screw rod (1); two high-strength nuts are mounted on the screw rod; and the two nuts are respectively a locating check nut (3) and an ascending-descending nut (4). Four special tools can form a set of special tool for dismounting the loaded tap changer oil tank of the universal transformer. The special dismounting tool is safe, flexible and reliable, has a simple structure and low cost, and is practical and effective.