The utility model discloses a segmental precasting assembly structure in a large bent cap. The structure comprises two precast segments and a cast-in-place segment, wherein the two precast segments are in butt joint through the cast-in-place segment, and prestress ribs penetrate between the two precast segments and the cast-in-place segment. The segmental precasting assembly structure has low requirements for bent cap precasting and on-site hoisting construction, and is particularly suitable for construction of the large bent cap.