The dewatering for foundation pit of sluice station is a significant and complicated issue. The water inflow volume of the foundation pit of Fenghuangjing Pump Station reconstruction for the diversion project from Yangtze River to Huaihe River was calculated using both the “large well method” and the numerical simulation method. The dewatering scheme was optimized via 3D seepage simulation, and the influences of the spatial arrangement of dewatering wells and the well depth change on the dewatering effect were compared and analyzed. A dewatering scheme was finally recommended in consideration of both economy and construction convenience. Under the premise that the dewatering meets the requirements of depth, the more uniform the spatial distribution of dewatering wells, the smaller gap between the pumping volumes of each well, the more conducive to unified pump allotment. Arranging the dewatering wells around the foundation pit and avoiding the layout of wells inside the foundation pit can reduce the interference to the construction, but can also raise the total pumping capacity. The greater the depth of the dewatering well, the greater the total pumping amount, and the fewer the number of dewatering wells that need to be arranged.