Abstract: The finite element model is established to investigate the development of deformation of enclosure wall during dewatering in a leaky aquifer by using ABAQUS on the basis of a practical pre-excavation dewatering test. The results show that when there is hydraulic connection between the inside and outside of a foundation pit, under the influences of an aquitard, the difference of pore pressure at both sides of enclosure wall (ΔP) increases first, then decreases, and finally tends to be stable during the pumping. As a result, the deformation of enclosure wall first increases, then decreases and finally becomes stable. However, when there is no hydraulic connection between the inside and outside of the foundation pit, ΔP increases monotonously and tends to be stable soon. The deformation of enclosure wall no longer first increases and then decreases, but increases monotonously.