Owing to the scarcity of surface water resources, groundwater is an important water source in the oasis belt of the southern margin of Tarim Basin. Thus, it is very important to systematically identify the distribution and origin of arsenic, fluorine, and iodine in groundwater in this area. Based on the detection results of 233 groups of groundwater samples from the oasis belt of the southern margin of Tarim Basin, the spatial distribution and hydrochemical characteristics of groundwater with high arsenic, high fluorine, and high iodine in different aquifers were analyzed, and the hydrogeochemical processes that affected the source, migration, and enrichment of arsenic, fluorine, and iodine in groundwater were further revealed by combining the geological and hydrogeological conditions with the groundwater occurrence environment in the study area. The levels of arsenic, fluorine, and iodine in groundwater were found to vary from 1.0-91.2 μg/L, 0.01-28.31 mg/L, and 10.0-2 637.0 μg/L, respectively. Groundwater samples with high arsenic, high fluorine, and high iodine accounted for 7.3%, 47.2%, and 11.6% of the total water samples, respectively, and arsenic, fluorine, and iodine co-enrichment accounted for 3.0%. Arsenic, fluorine, and iodine co-enriched groundwater was found to be mainly distributed in Minfeng County in the middle of the study area, and the Cl·SO4-Na type was identified as the main hydrochemical type. Groundwater fluorine and iodine levels significantly increased from the recharge zone to the transition zone and then to the evaporation zone. Further, arsenic levels were greater in both the transition and evaporation zones. The sampling points for arsenic, fluorine, and iodine co-enrichment in groundwater were mainly distributed in the shallow confined aquifer of 36-60 m. Shallow groundwater was affected by evaporation and mineral dissolution and precipitation, which increased with an increase in the arsenic, fluorine, and iodine enrichment terms. Quaternary aeolian deposit had a remarkable influence on fluorine content, while pluvial- lacustrine deposit had a great influence on arsenic and iodine content. Altogether, fine-grained lithology, gentle terrain, shallow burial conditions of groundwater, slightly alkaline groundwater environment, and mineral dissolution mediated by organic matter under microbial degradation were the main mechanisms conducive to arsenic, fluorine, and iodine co-enrichment.