The safe password lock principle, the number lock on the safe holds the key to unlocking. The common number lock has three groups of unlock numbers, and each group has two digit numbers. There are three rotating discs (wheels) inside the three sets of number locks, each of which has a notch. According to a certain operation method, turn the dial (dial) left and right so that the three sets of numbers are respectively aligned with the dial outer ring. The fixed mark line, through the transmission device to drive the three discs to rotate, can make the gaps on the three discs in a straight line at the design position, so that the beam that drives the latch falls into the gap of the three discs, and the door can be Opening (the number lock with the drive wheel disc is that after the beam falls into the gap of the disc, the push-pull hook on the beam can be hooked on the push-pull gap of the drive cam (disc), and the lock can be pulled back and unlocked.