The present invention discloses a cover device used to cover the built-in valve mounting channel port of IBC and a container. The IBC comprises a side plate, a base and a channel located in the base and used to receive the built-in valve. The cover device comprises a cover and structures or components used to detachably connect the cover to the side plate over the channel. The cover can be installed on the base at the position adjacent to the side plate, and can be rotated around a rotational axis of the cover itself, so as to open or cover the channel port. The cover is further provided with a lock hole, and the base is provided with a locking slot, so that the cover can be locked to the base by a disposable lock. The cover device of the present invention has a simple structure and is easy to operate. Further, it can well achieve the effect of dust-proof and/or thief-evident.