The invention relates to a fast-assembly spacer ring connecting structure, is applicable to connection of membrane discs with a relatively small shaft head distance and an inverted penetration structure, and belongs to the technical field of machinery. The fast-assembly spacer ring connecting structure comprises a first half spacer ring and a second half spacer ring, wherein after being assembled through radial insertion, the first half spacer ring and the second half spacer ring form a whole circle; connector parts of the half spacer ring and the second half spacer ring are Z-shaped lap joint structures; and the Z-shaped lap joint structures can be spliced. According to the fast-assembly spacer ring connecting structure, the structure is simple, a traditional whole circle spacer ring is divided into two half spacer ring parts through the Z-shaped lap joint structures, the two spacer rings can be assembled in a radial insertion manner, a unit device does not need to be moved, the assembly is simple and quick, the mounting difficulty of a short wheelbase membrane disc coupling is greatly reduced under the precondition that the utilization performance is not influenced, and the mounting quality of a shafting is improved.