Antitheft well cover lock

The invention discloses an antitheft well cover lock. The antitheft well cover lock comprises a special T-shaped inner triangular key, a lock body, a locking disc and plastic steel lock tongues. The lock is fixed in the center of the lower surface of a well cover; the special inner triangular key is inserted in a triangular cylinder of the locking disc by penetrating through the center of the well cover, and is downwards vertically forced to open a locking mechanism; meanwhile, the key is clockwise turned in place; a linkage mechanism controlled by the key drives four plastic steel lock tongues to synchronously retract in four directions below the well edge in a cross coordinate manner; and the well cover is opened. Conversely, the special inner triangular key is still inserted in a locking hole of a lock core mechanism by penetrating through the center of the well cover, and is downwards vertically forced to open the locking mechanism; meanwhile, the key is anticlockwise turned in place; the linkage mechanis