The invention discloses a construction method for dismantling a temporary underground continuous wall. The construction method comprises the following steps: dismantling the temporary underground continuous wall till the interior of a bottom soil body below a bottom cushion layer of a foundation baseplate; backfilling the bottom soil body till the bottom cushion layer of the foundation baseplate; filling the bottom cushion layer of the foundation baseplate; and enclosing the foundation baseplate. According to the construction method disclosed by the invention, the bottom of the temporary underground continuous wall is dismantled till the interior of the bottom soil body below the bottom cushion layer of the foundation baseplate, and the rigidity of the bottom structure positioned at the temporary underground continuous wall of the foundation baseplate is reduced through soil backfilling, thereby reducing tension cracking, caused by non-uniform settlement, of the foundation baseplate. Furthermore, the integrity of the foundation baseplate can be guaranteed and underground water leakage can be prevented when the foundation and operation safety is guaranteed.