The invention relates to the technical field of production of impulse turbines, in particular to a manufacturing method of a large water distribution ring pipe. The manufacturing method of the large water distribution ring pipe comprises the following steps: (1) blanking: blanking clean materials in each cylinder body; spreading each cone body and blanking into a sector surface, bisecting inner and outer arc length and marking a centripetal a cold press line on the surface of steel plate; and strictly controlling the clean material line dimensional tolerance; (2) performing cold press molding: performing cold press molding by a segmenting and sectioning self-made mould; (3) checking and performing profile correction after the cylinder body and the cone body are molded: placing ground sample according a ratio being 1:1, labeling the positions and punching; performing local flame heating or external mechanical force correction; and strictly controlling the forming size and diameter tolerance of a single section of cylinder body to be +/-2mm; (4) guaranteeing accurate intersecting line mouth shape of the welding position of each section of cone body; (5) taking measures to prevent deviation of construction site butting welded junction position and guarantee qualified size of a flange face; and (6) checking whether the product is qualified or not: self-making a pressing mould after integral welding and performing a high-pressure water pressure test. The manufacturing method of the large water distribution ring pipe is simple and practical, easy to operate, high in production efficiency, low in cost and excellent in product quality.