The precipitation can provide a good construction environment for the excavation of the foundation pit, which has significant effects on the stabilization of the surrounding soil, the stability of supporting structure and the reduction of hydraulic pressure.At the same time, precipitation can lead to complicated seepage field of foundation pit, which may cause disasters such as flowing soil, flowing sand, piping, and etc. Ground subsidence also can be caused because of the soil consolidation induced by the fall of the groundwater level in the foundation pit.Therefore, attentions must be paid to the influence of foundation excavation and dewatering on the foundation pit itself and its surrounding buildings. Taking a foundation pit project in Shanghai as an example, this paper establishes a numerical groundwater seepage model according to the site conditions of engineering geology and hydrogeology, design depth of enclosure structure and pit excavation of metro station. Then, a pumping operation plan is tested and adjusted using the model to guide the construction safely and smoothly, which provides references for the design and construction of the same type of foundation pits.