The utility model provides a shaft mouth structure which comprises a blowout control box, a sealing device, a middle-high pressure gas injection device and a well pipe. The middle-high pressure gas injection device comprises a first communication pipe and a first gas injection pipe which is communicated with the first communication pipe. The blowout control box, the sealing device, the first communication device and the well pipe are sequentially arranged and communicated with one another. A continuous oil pipe enters from the blowout control box and then enters the well pipe sequentially through the sealing device and the first communication pipe. The first gas injection pipe is communicated with an outer gasifying agent source through a middle-high pressure gasifying agent pipeline. A middle-high pressure gasifying agent enters the first communication pipe through the first gas injection pipe and then enters the well pipe. The shaft mouth structure is reasonable in design and simple in structure, the down-pass operation of the continuous oil pipe can be achieved, and it is guaranteed that the whole operation process is simple, convenient and safe.