The utility model discloses a hidden type airtight floor door which comprises a door frame, a cover plate, a fence mechanism, a driving piece, a door lock mechanism and an opening mechanism, one side of the cover plate is hinged to the door frame, one side of the fence mechanism is hinged to the door frame, the other side of the fence mechanism is hinged to the cover plate, and the fence mechanism forms a fence structure on the side edge of the door frame. The fence mechanism forms a folding structure in the door frame, the driving piece is connected with the cover plate and used for driving the cover plate to rotate, the door lock mechanism is arranged between the cover plate and the door frame, and the opening mechanism is installed on the inner side of the door frame and connected with the door lock mechanism. A linkage structure is formed by the fence mechanism and the cover plate, that is, movement of the fence mechanism is triggered by the cover plate, so that the problem of interference of movement of the cover plate and the fence caused by driving of an independent oil cylinder structure is avoided, the cover plate can be locked to the door frame by arranging the door lock mechanism, and the opening mechanism can be opened when the door lock mechanism cannot be unlocked from the outside. And the door lock mechanism is unlocked on the inner side.