The invention relates to the technical field of metal pipe fitting connection, in particular to an optimization connecting structure of metal pipe fittings and an implementation method thereof. The structure comprises the pipe fittings, multi-functional plugs arranged in inner holes in the tail ends of the pipe fittings, and connecting pieces connecting the pipe fittings. The peripheries of the connecting portions of the pipe fittings are provided with radial through holes, and a center connecting line of the through holes is parallel to the end faces of the pipe fittings. Each multifunctional plug comprises a plug body at the tail end, a groove or through hole in the middle, a large positioning step and a small positioning step which are located at the top end, wherein the outer end face of the large step is provided with an axial through hole or through groove communicated with the groove. Each connecting piece is of a casting-forging composite structure, and inner and outer layers of metal rings and a plurality of radial and axial metal posts connected with the metal rings are formed through forming carried out in a casting-forging mold. Pipe fitting and plug forging connection portions machined in a casting-forging mode are covered and connected in a forging mode in the three-dimensional direction to form an integral structure. High-toughness connection of a bicycle frame and pipe fittings of a front fork is thoroughly achieved.