Dewatering prior to foundation pit excavation is a critical measure to prevent engineering hazards such as slope instability at the pit top, seepage around the pit, and bottom heave. As a key parameter in dewatering design, hydraulic conductivity directly influences the risk control in foundation pit engineering. Based on the east anchor foundation pit project of the Shiziyang Passageway, single-well pumping tests and stratified multi-well pumping tests were conducted. The water level variations in the internal dewatering wells and the external observation wells were monitored in stages. Accordingly, a finite difference numerical model for the pumping tests was established. The hydraulic conductivities of the target aquifers obtained through the classical analytical method were used as the initial parameters of the numerical model, and the hydraulic conductivities of each stratum were determined through back-analysis. The results indicate that the water levels in the external observation wells do not decline synchronously with the internal pumping process, which demonstrates that there is no leakage at the joints of the circular diaphragm wall. The significant differences in water level drawdown among the internal dewatering wells suggest that the power and operation time of the pumping equipment should be differentially adjusted based on the characteristics of the strata where the dewatering wells are located, to achieve an overall uniform dewatering effect. The absolute value of the relative error between the field observation values and the calculated values of the reconstructed finite difference model is 11.58% on average, which validates the reliability of the combined classical analytical and finite difference method. This analysis method provides a reference for the back-analysis of hydrogeological parameters in deep foundation pit engineering.