The invention relates to a post-cast strip supporting structure and a construction method thereof. The method includes the steps that a supporting pipe and head sealing plates are selected according to the actual situations; the position of the pre-buried supporting pipe is obtained through calculation; the head sealing plates are welded to the two ends of the supporting pipe for opening sealing;positioning is performed on a beam bottom plate, the position of a concrete supporting column is determined, and paying-off and holing are performed on the beam bottom; after supporting is finished onthe beam bottom plate of an on-site structure, the supporting pipe is lifted for positioning and installation; and final random check is performed on on-site installation. By means of the post-cast strip supporting structure and the construction method thereof, the post-cast strip supporting effect is improved, the construction period is short, and cyclic utilization is allowed at the later stage.