The present utility model relates to municipal water supply and drainage engineering construction, and to a fragmented prefabricated structure of a deep and large open caisson, comprising a plurality of uniform arcuate pipe segments in a rectangular shape. The plurality of arcuate pipe segments, after being connected to each other, can define an annular shape on the horizontal surface to form an open caisson in the vertical direction. Arcuate bolt holes are respectively reserved in the upper and lower ends and the left and right side walls of each arcuate pipe segment, and two adjacent bolt holes can be in a through connection. Two adjacent arcuate pipe segments are connected to each other by means of an arcuate bolt. Anchor rod holes are formed in the front surfaces of the arcuate pipe segments, anchor rods are provided on the anchor rod holes, and the arcuate pipe segments are fixed to a foundation pit wall by means of the anchor rods. The arcuate pipe segments are of a concrete structure. By using this apparatus for cast-in-situ in sections and then sinking, the original open caisson operation construction technology is changed from cast-in-situ to prefabricated structure construction, which is especially suitable for the production of open caissons in rounded gravel areas having limited construction clearance, large groundwater consumption and soft geology; in addition, the construction cost is reduced and the construction quality is improved.