The invention discloses a closed enclosure system comprising supporting piles with specially-shaped sections and a construction method thereof. According to the system, a water-soil pressure is born by cast-in-place piles with cross-shaped or T-shaped sections, a space among the supporting piles with the cross-shaped or T-shaped sections is closed by cement-soil piles, and bearing and water stopping are integrated; the cast-in-place piles with the cross-shaped or T-shaped sections and high flexural rigidities are used as the supporting piles, and compared with the traditional supporting piles with circular sections, the overall rigidity of a supporting system can be remarkably increased, the displacement of a foundation pit can be reduced, and the engineering cost can be decreased; the space among the supporting piles is closed by the cement-soil piles, and a closed water-stopping curtain does not need to be additionally arranged, so that the engineering cost can be remarkably decreased; in the enclosure system, the piles with the cross-shaped sections or the piles with the T-shaped sections are engaged with the cement-soil piles at flanges, and compared with the engagement between the existing cast-in-place piles with circular sections and cement-soil piles, each lap-joint part has a long rounded flowing path and a good water-stopping effect; and the enclosure system disclosed by the invention is capable of obtaining a supporting effect which is similar to the supporting effect of an underground diaphragm wall enclosure structure, and low in construction difficulty and engineering cost.