Abstract: The differential settlement of the hanging and footwall walls is the main activity mode of ground fissures in Xi'an. It is well accepted that the extraction of groundwater in confined aquifer is an important factor aggravating the differential settlement. The specific mechanism is not quite clear though. To clarify the mechanism,we performed the stress condition analysis and the soil-ground fissure coordinated deformation analysis on horizontal units,carried out numerical simulation,and explained how deformation differs by wall. Through fluid-structure coupling numerical simulation,we obtained settlement characteristics on the ground by different pumping condition and ground fissure permeability. The result shows that,the small-shear-modulus ground fissure causes relatively larger load on the top and larger reaction force on the bottom for units of hanging wall,nearby the fissure. However,when it comes to those of footwall,the situation is just the opposite. This is the foremost reason that the settlement is relatively larger in the hanging wall. Pumping condition and ground fissure permeability have influence on the mechanical disturbance caused by water-pumping,enlarging the deformation difference between two walls. The differential settlement is obvious when the well is located in the hanging wall,and more visible when the permeability of the ground fissure is poor.