The invention provides a key mounting base, and belongs to the field of security door facilities. The key mounting base comprises a fixed plate and a sliding seat, and the sliding seat is slidingly connected to the fixed plate. An inserting hole is formed in the sliding seat, and the direction of the inserting hole is consistent with the sliding direction of the sliding seat. A through hole for allowing a key to be inserted in is further formed in the sliding seat, and a locating hole matched with the through hole is formed in the fixed plate. A limiting block is arranged on the fixed plate, and used for limiting separation of the sliding seat and the fixed plate. The key mounting seat can be mounted behind a security door and can be used for allowing the key to be mounted, and therefore the key can be conveniently placed behind the security door, a user can remember to take the key when going out, and the situation that the user forgets to take the key when going out is completely eradicated.