In order to reveal the impacts of dams and reservoir works located in the arid zones on the groundwater level of the middle and lower reaches of the Qarqan River, with GMS applied to the groundwater modeling, a model for prediction studies of the changes in the groundwater flow field was made on the basis of the related data, such as hydrogeology, climate change and irrigation in local areas. The analysis results indicate that firstly, the equilibrium amount of the groundwater in the simulated area of the Qarqan River has been 1170.74*10~4 m~3 for years, showing slight proper equilibrium. The rising height of the groundwater has been up to 13 mm for years, and the groundwater has generally demonstrated upgrade tendency; and secondly, from the perspective of the whole region, great changes of groundwater flow field trend have not appeared since the dam was constructed. However, remarkable changes of flow field in the local areas have occurred. The main areas are irrigated ones and the downstream sub-basin of the lakes. The fluctuation of the affected underground water level is up to 0.4 ~0.8 m, whereas the likely affected width range close to the north and south sides of the Qargan River is about 1 km.