The invention relates to a valve locking mechanism for controlling a fluid medium and belongs to the field of fluid control valves. A general flat key, a locking wheel and two ratchets and the like are sequentially placed on a valve rod above a lower flange. An upper flange and the lower flange are connected through a plurality of hexagon socket cap screws and pressed on a sleeve and two step shafts; and the two flanges are connected with the hexagon socket cap screws. The pair of symmetrical ratchets is arranged, the two ratchets have a self-locking function when in a locked state; one ratchet is used for preventing the locking wheel from rotating clockwise, and the other ratchet is used for preventing the locking wheel from rotating anticlockwise. Each ratchet is a lever part, the driven side is the tooth surface and a tooth body of the ratchet, the driving side is in a shifting fork shape, the middle of the ratchet is provided with a cylindrical hole, and the cylindrical hole is used for being matched with step shaft positioned through the cylindrical hole. A shaft is arranged, the middle section of the shaft undergoes trimming and tapping, and the hexagon socket cap screws or hexagon socket flat end fastening screws are installed to serve as parts for pushing the ratchets to rotate during the locking.