The invention discloses a combined anti-theft mechanical lock and a key for opening the combined anti-theft mechanical lock. The problem that in the prior art, an existing mechanical lock is not high in safety performance is solved. The combined anti-theft mechanical lock comprises a lock shell, a mechanical lock device arranged in the lock shell and a positioning driving device used for driving the mechanical lock device; the mechanical lock device comprises a ratchet mechanism; one face of the ratchet mechanism is provided with at least one protruding column; the positioning driving device and the protruding column are located on opposite sides of the ratchet mechanism; a ring disc and a protruding disc matched with a blind hole are sequentially arranged in the position, on the protruding column side, of the lock shell; and a groove matched with the protruding column is formed in the ring disc. By means of the above scheme, the aim of being high in safety performance is achieved, and the very high practical value and popularization value are achieved.