Combined with construction of north anchorage caisson, field pumping tests were carried out. Permeability coefficient was acquired for dewater sinking. Water yield of single well and total water inflow of caisson excavation were calculated. It is found that the measured amount of total water inflow is slightly larger than the theoretical value. Based on effective stress principle, the compression of phreatic water aquifer caused by dewater is almost negligible，and the ground settlement is mainly composed of confined water aquifer compression. The calculated settlement curve along the levee was in good agreement with the measured data.