The invention relates to a bullet storing and firing mechanism for a bullet storage cabinet. The mechanism is characterized by comprising a shell for storing a bullet box, wherein the interior of the shell is partitioned to a front bullet box storage chamber and a back bullet box storage chamber by a partition plate which is arranged vertically; a moving plate capable of sliding back and forth penetrates in the bottom of the shell; a replaceable block of which the appearance is matched with that of the bullet box is fixed on the moving plate; the front side wall and back side wall of the shell are provided with a front outlet and a back outlet respectively; and a middle outlet for the replaceable block to go in and out is opened on the partition plate. When the moving plate moves back and forth, the replaceable block exposes the bullet box located at the bottom of corresponding storage chamber, and the exposed bullet box can move out via the front outlet or the back outlet; meanwhile, the bullet storage cabinet used for the mechanism can fire bullet without opening the cabinet door, thus the security in using and storing the bullet can be greatly improved, automatic management of the bullet firing process is possible, and the mechanism is suited to be promoted and used in the bullet storage cabinet.