Abstract: Restoration of soil water in alfalfa-grain crop rotation fields was observed and simulated in the semi-arid region of southern Ningxia by the combination of field investigation and crop model simulation. Results showed that: a high soil desiccation rate and soil water restoration rate appeared both in the earlier stage and a low rate appeared in the later stage in the process of formation of desiccation layer during alfalfa growth period and soil water restoration during alfalfa-grain crop rotation period. It was difficult to restore soil water in the 8-10 m layer soil. Considering the sustainable soil water use of alfalfa-grain crop system, PPW rotation system (with the sequence of potato, potato, spring-wheat) was the optimum pattern to restore soil water on desiccated alfalfa grasslands with 6-8 years old, and alfalfa can be planted again after PPW rotation for 16-20 years. Results of this study can provide references for the using and restoration of soil water in alfalfa land on the semi-arid area of the Loess Plateau.