Combined with a deep foundation pit project of a rainwater storage tank in Hefei city, a simulation has been made of the whole construction process by using MIDAS three-dimensional finite element software, followed by a comparison as well as an analysis of the internal force and displacement deformation laws of the support structure under the “pile-wall integration” supporting structure and the traditional temporary supporting structure during the foundation pit excavation. The results show that the deformation of retaining piles of traditional temporary structures is 1.74 times that of new structures in terms of deep horizontal displacement; in terms of bending moment, the deformation of the retaining pile of the traditional temporary structure is 3.64 times that of the new structure, with the deformation of the basement exterior wall being 5.08 times that of the new structure; in terms of shear force, the deformation of the retaining pile of the traditional temporary structure is 2.72 times that of the new structure, with the deformation of the basement exterior wall being 4.88 times that of the new structure. This result shows that the“pile-wall integration”structure helps to greatly improve the overall stability of the foundation pit, which makes it necessary for an application of the permanent retaining pile technology in practical projects.