The utility model relates to an anti-theft plug which is of a cylinder structure with an external thread on the outer circumference surface, wherein the outer end face of the plug is provided with a blind hole. The utility model also relates to a special dismounting tool for dismounting the plug. The special dismounting tool comprises a dismounting head matched with the blind hole on the anti-theft plug and a handle connected with the dismounting head, wherein the dismounting head comprises a core body, a driving lever and two tile-shaped locking pieces; the core body is formed by two same tiles with same arc-shaped outer circumferential surfaces which are alternatively buckled into a whole and have parallel axial lines; and the inner circumferential surface of each locking piece is an arc surface, the outer circumferential surface of each locking piece is provided with ratchets distributed along the circumferential direction, the inner circumferential surfaces and the outer circumferential surfaces with the ratchets of the locking pieces are eccentrically arranged, the locking pieces are in sliding matching connection with the tiles correspondingly, and the larger inner end faces on the locking pieces are arranged corresponding to gear surfaces. The anti-theft plug provided by the utility model is completely screwed in the hole, has an outer end face which is aligned to the hole end, and can be dismounted by only using the special tool.