The invention relates to the technical field of gas turbines and provides a gas turbine transition section structure. The gas turbine transition section structure comprises an upper wall and a lower wall, the outlet end of the upper wall is separated from the outlet end of the lower wall and the upper wall and the lower wall are each of a fan shape. Side sealing elements are arranged at the outer sides of the upper wall and the lower wall and enable sealing to be achieved between the two sides of the upper wall and the lower wall; first connecting pieces are fixed on the upper wall and used for fixedly connecting the upper wall and a turbine inner casing; limiting pieces are fixed on the lower wall and used for limiting the radial movement of the lower wall; the side sealing elements comprise second connecting pieces used for connecting with the turbine inner casing. The gas turbine transition section structure can effectively prevent an opening of an outlet end of a transition section from getting smaller as a result of a ratchet effect, and complexity of the structure is reduced, so that the disassembly is facilitated. In addition, as an original side wall structure prone to be deformed due to heat stress does not exist any longer, side wall warping and even fracture at the outlet end of the transition section structure caused by low-cycle fatigue as well as dropping of a sealing structure are avoided; air is prevented from entering a thermal channel directly.