The invention discloses a spoiler assembling structure and an assembling method thereof. The spoiler assembling structure comprises a first ring, a second ring and a spoiler. A first pin hole is formed in the first ring, a second pin hole is formed in the second ring, a first pin and a second pin are arranged at the two ends of the spoiler, the diameter of the first pin is smaller than that of thefirst pin hole, and the diameter of the second pin is equal to that of the second pin hole. A metal sleeve is arranged between the first pin and the first pin hole, the internal diameter of the metalsleeve is equal to the external diameter of the first pin, the external diameter of the metal sleeve is equal to the internal diameter of the first pin hole, and the height of the metal sleeve is equal to the length of the first pin. No axial force is applied to the spoiler in the assembling process of the spoiler, it is avoided that the spoiler is scrapped due to plastic deformation, the production cost is effectively reduced, meanwhile, the mounting quality of the spoiler is improved, production delivery of a gas turbine is guaranteed, and the effective assembling structure and the mountingmethod convenient to operate are provided in order to solve the problems about assembly of parts of the structures.