Mold device for prefabricating large-diameter concrete pipeline, mounting method and prefabricating method

The invention discloses a mold device for prefabricating a large-diameter concrete pipeline, which comprises a cylindrical outer mold formed by splicing a plurality of outer mold sections and a cylindrical inner mold formed by splicing a plurality of inner mold sections, and a roundness adjusting assembly for adjusting the roundness of the inner mold is arranged between the inner side surfaces of two adjacent inner mold sections. The roundness adjusting assembly comprises a horizontal double-end reverse-thread screw and two connecting rods, the axes of the two connecting rods coincide with the axis of the double-end reverse-thread screw, and one end of each connecting rod is fixedly connected with the inner side face of one inner mold section. A threaded blind hole is formed in the other end of each connecting rod and is in threaded connection with one end of the corresponding double-end reverse-thread screw, an annular boss extending inwards is arranged at the bottom end of the outer mold, and the bottom of