The invention discloses an internal grouping type winding water-blocking system for a high-density optical cable, wherein the system comprises a twisting table and a casing pipe yarn winding unit; the casing pipe yarn winding unit comprises a pay-off head matrix, a yarn winding machine and a guide wheel, and the pay-off head matrix is provided with a plurality of casing pipe wire spools; the yarn winding machine comprises a machine frame, a motor, a main fixed shaft barrel, a flying shuttle rotating barrel, a movable ring mold base, a yarn ball rotating barrel, a flying shuttle and a yarn guide pipe; the flying shuttle rotating barrel is mounted on the inner side of the main fixed shaft barrel through a first bearing, a rotating shaft of the motor is connected with the first end of the flying shuttle rotating barrel, and the movable ring mold base is mounted at the second end of the flying shuttle rotating barrel; and the yarn ball rotating barrel is mounted on the outer side of the main fixed shaft barrel through a second bearing, the flying shuttle is mounted on the movable ring mold base, the yarn guide pipe is mounted on the flying shuttle, and the guide wheel is mounted on a supporting frame. According to the invention, a grouping type winding mode is adopted, and physical yarn winding isolation is completed on grouped casing pipe groups, so that identification is facilitated; and a casing pipe is woven by water-blocking yarns in a winding mode, isolation and water blocking are achieved, tension is small, optical fibers in the casing pipe cannot be damaged, and use is quite reliable.