"Change drainage to impoundment" is a significant innovation in saline land management. To expose mechanism of salt suppression by water cycling between the waterbody in the ditch different in impounded level and the soil of the neighboring ridges, a home-made apparatus was used to simulate salt movement between waterdody and soil for the study of laws of salt movement in the soil profile. It was found that regular changes in water level was an important factor driving salt movement in the soil. With the water level lowering from 70 cm to 40 cm and further to 20 cm, soil salt gradually dissipated from the 0～65 cm soil layer into the waterbody, and then back into the 65～100 cm soil layer, thus changing the soil salt in vertical distribution and suppressing the salt downwards in the profile. For the study, a mathematical model for simulation of salt movement in the soil using the Hydrus-2D software. Analysis and comparison demonstrated that the simulation was basically consistent with the experiment in result, land the model worked well in simulation. Therefore, the mechanism of salt suppression by cycling water between the waterbody and the soil along with changes in water level is solid, and the model of “changing drainage into impoundment” for management of soil salt is workable for amelioration of salt-affected soils.