The formation conditions are complex in an intercity railway station of Zhengzhou to Xinzheng, lens of sandy soil and cohesive soil exist interacted. The excavation range is in poor permeable loess formation with silt, silty sand silty clay, so the dewatering well construction quality is very important. The formation conditions and characteristics of enclosure structure should be fully considered in dewatering design to ensure water level lowering below the excavating surface and avoid the sand flow, piping and gushing. The dewatering scheme is designed on the baisis of the analysis on hydrogeology seepage in the field by 3D numerical simulation, and with the effective dewatering construction measures being used, good dewatering effect has been proved by practice.