A cylinder lock assembly includes a lock cylinder inserted into a cylindrical chamber of a lock housing, the lock cylinder being formed with plate mounting slots, a latch slot, and a main key slot; primary locking plates inserted in the respective plate mounting slots, each of the primary locking plates being formed with a secondary plate recess, a first key slot, and a first latch groove; secondary locking plates inserted in the respective secondary plate recesses, each of the secondary locking plates being formed with a second key slot and a second latch groove, springs being provided between the primary locking plates and the lock cylinder and between the secondary locking plates and the lock cylinder respectively; and a latch inserted into the latch slot, a latch return spring being provided between the latch and the lock cylinder.