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Datong Basin in China is a typical arid-semiarid inland basin, with high levels and wide distributions of arsenic (As), fluoride (F-), and iodine (I). To better understand the presence of low-quality groundwater in Datong Basin and assess the health risks for local residents, groundwater samples were collected from the shallow aquifer and in medium-deep groundwater and analyzed for As, F-, I, and nitrate (NO3-). Maxima of 1932 mu g/L for As, 80.89 mg/L for F-, 2300 mu g/L for I, and 3854.74 mg/L for NO3- were detected in shallow groundwater, which greatly exceeded the WHO limits for drinking purpose. High-As groundwater was present in both shallow and medium-deep aquifers. High-F- and high-NO3- groundwater was widely distributed in the shallow aquifer, and high-I groundwater was mainly present in the medium-deep aquifers. Poor-quality groundwater in the Datong Basin is mainly caused by local geological and climatic conditions, which are characterized by strong evaporation, active water-rock interactions, thick lacustrine sediment, low groundwater flow rate, and reducing and weak alkaline environments. However, groundwater quality was further impacted by agricultural activities in some areas, as shallow groundwater was also polluted by nitrate. Datong Basin inhabitants face high health risk caused by high concentrations of As, F-, I, and NO3-. The mean noncarcinogenic risk values (HQ(total)) were 18.40 for children, 10.94 for adult females, and 9.47 for adult males due to exposure to contaminants in shallow groundwater; and 13.76 for children, 8.18 for adult females, and 7.08 for adult males because of exposure to medium-deep groundwater. Further, the carcinogenic risks (CR) caused by exposure to As were very high for local inhabitants, with the mean and median CR values of 4.20x10(-3) and 4.13x10(-4) in shallow groundwater and 3.44x10(-3) and 1.71x10(-4) in medium-deep groundwater, respectively.