In northern China, getting water in well field nearby a river is a common way to extract ground waterfrom aquifer. However, the hydraulic disconnection between the groundwater and the river water often occurs in aridseasons because of decrease of ronoff in the river. The experiment with a sand-box model is used to investigate thedevelopment of the hydraulic disconnection. Two computation models for single satUrated simulation and saturated-unsaturated simulation are used to prove the laws of the hydraulic disconnecton obtained by the experiment.Somenew understandings are got:(a) the disconnection point is in the water-bearing layer beneath river-bed;(b)two saturated zones exist under the river-bed, and one of them is suspended zone touching with river water and the another is water fable.