The method of double-sides-wall drift is usually adopted when shallow buried large section tunnel is excavated,and the core rock is a quite important factor to the displacement stability of the surrounding rock mass and the internal force of supporting during excavation. Based on a subway tunnel(Beibei station) in Chongqing,FLAC3 d is used to simulate shallow buried large section tunnel with method for the of double-sides-wall drift and construction method for the core rock. The change of surrounding is compared and analyzed before and after reserving core rock. It was found that a reasonable design of core rock can reduce the stratigraphic sedimentation rate and improve the stress distribution of surrounding rock. Meanwhile,the arch protection method and the temporary backfill slurry method have a good effect on the reinforcement of landslide.