The invention discloses a large double-pumping-set unit assembling device and a construction process. The large double-pumping-set unit assembling device comprises a water delivering tube, channel steel, a tube support, a reducer tube, a water pump, a first fixing seat, an eccentric tube, a rubber soft joint, a Y-shaped filter, a second fixing seat, a butterfly valve, first bolts, damping bridges,second bolts and supporting legs, wherein the first fixing seat and the second fixing seat are fixed on the bottom of the channel steel separately through bolts; the damping bridges are correspondingly mounted on the top of the first fixing seat; each first bolt is connected between the corresponding damping bridge and the water pump; each second bolt is connected between the corresponding damping bridge and the channel steel; the water pump is arranged on the tops of the two damping bridges; the two sides of the water pump are separately movably connected with the eccentric tube and the reducer tube through flanges; and one end of the eccentric tube is connected with a rubber soft joint. By the large double-pumping-set unit assembling device, stability, quality and safety of a modular frame are improved favorably, the construction period can be shortened effectively, and the engineering cost is reduced.