In view of the characteristics of the deep foundation pit of a long and narrow irregular-shaped metro station in the Nanchang area—where the upper portion consists of loose miscellaneous fill and the lower portion is a water-rich confined aquifer with high permeability—an analysis was systematically conducted on the surface settlement and support structure response of a metro station foundation pit under the influence of groundwater seepage and surface precipitation, in combination with real-time monitoring data. By comparing three-dimensional numerical simulations with field measurement data, the accuracy of the established model and the reliability of the analysis method were verified.It was shown that the deformation characteristics of the retaining structure generally exhibited a "bow"-shaped bending toward the interior of the foundation pit, specifically characterized by smaller displacements at both ends and larger displacements in the middle. The maximum horizontal displacement was observed at a distance of 15 m from the edge of the foundation pit, approximately half of the excavation depth (0.5H), with values ranging from 0.0119H to 0.0659H. The surface settlement around the foundation pit followed a parabolic distribution, with an influence range of about 1.0H. The maximum settlement point was located at a distance of 0.275H from the pit edge, with a settlement magnitude of approximately 0.028%H. Furthermore, significant differences in surface settlement were observed among different areas, following the pattern: standard section > end well > irregular corner. Moreover, the simulation results were able to satisfactorily reflect variations in the axial force of each support and demonstrated good agreement with the measured data. The research results can provide a scientific basis and theoretical support for the safe construction of similar foundation pit projects.