The open-cut section of a river-crossing tunnel in Nangjing is a super deep foundation pit with think and high water permeability sand layer， where the aquifer is massively thick with large permeability coefficient， and recharged by the Yangtze River. The hanging type water cut-off curtain was used for the foundation pit due to very large water inflow. During the construction of the dewatering well， it was found that the original dewatering scheme cannot meet the requirements for dewatering through well developemt with high deviation. In order to ensure the safety and smooth construction of the foundation pit， in-situ pumping test was carried out while drilling the dewatering well. Through analysis of the test data， and parameter inversion and dewatering simulation using the three-dimensional numerical method， adjustment was made in time on the diameter， number and pump configuration of the dewatering wells in the JD1 and JD2 sections with large excavation depth . The inverted parameters of the pumping test for the foundation pit were much larger than those of the original scheme. The actual water inflow of the foundation pit was as high as 91000 m³/d， which was 2.2 times of the estimated value of 42000 m³/d of the original dewatering scheme. With the timely and proper adjustment of the dewatering scheme， the water level in the pit was reduced below the base with little increase in the total number of wells， which ensured the smooth implementation of the foundation pit， fully demonstrating the importance of dynamic adjustment of pumping test and the pumping test scheme in dewatering.