On the basis of sufficient discussion of hydrogeologic condition of geothermal water in the Xaoquan area, authors a mathematical is studied with MODFLOW model is established, and then the geothermal water is studied with MODFLOW program. Andthe mathematical model is identified. The authors compare the simulative water level with actual water level. The MODFLOW program can study geothermal water,when the simulative water level approximated to actual water level, and the mathematical MODFLOW model is right. Geothermal water under condition of different exploitation is stndied with the MODFLOW program. Sustainable exploitation is achieved.