A mouth structure of the gas storage well is characterized in that thata full thread control structure having a third stage junction, bivalve, and double safety locks is adopted, comprising a casing head 1 which is connected with a casing coupling 10 in a threaded connection way; a gasin and gasout joint 2 is a metal short piece which is connected with a first stage casing head 1 also in a threaded connection structure which serves as a transition joint between a first stage and a third stage; thus the connecting direction of the process line can be changed as will, and the connection of the pipeline is facilitated. The side of the gasin and gasout joint 2 is connected with a gasin and gasout pipe 12,and the gasin and gasout pipe 12 are connected with a gas incoming and exhaust valve 6 and a gas incoming and exhaust service valve 7. The top of the gasin and gasout joint 2 is connected with a blow down joint 3; the blow down joint 3 is connected in order with a blow down service valve 5 and a blow down valve 4. The inner of the blow down joint 3 is a bullet. The top of the blow down joint 3 is fixed with a compression nut 18. With a press hat type internal cone sealing, a damage caused by opening a first stage casing head can also be avoided, meanwhile, servicing is more convenient and reliable, good in air tightness, and uneasy in distortion, and is insurable that the casing head 1 can not be damaged.