Abstract: Groundwater inorganic nitrogen pollution is one of the most prevalent water environmental problem in Jianghan Plain. Agricultural activities are an important source of inorganic nitrogen in groundwater. However, in agricultural areas with dense river networks, it is urgent to strengthen research on the pollution sources and migration and transformation mechanisms of inorganic nitrogen in shallow groundwater recharged by rainfall and surface water. Taking agricultural area of the eastern Jianghan Plain as an example, the chemical characteristics, the source of inorganic nitrogen and its migration and transformation mechanism of surface water and groundwater were analyzed by hydrochemistry combined with hydrogen and oxygen isotopes and strontium isotopes. The results showed that the cations of surface water and groundwater samples in the study area were dominated by Ca²⁺ and Na⁺, and the anions were dominated by \mathrmHCO_3^- . The water chemical type were dominated by-HCO₃—Ca·Na and HCO₃—Ca The inorganic nitrogen in surface water and groundwater was mainly nitrate, and the concentration of inorganic nitrogen in groundwater was significantly higher than that in surface water. The groundwater samples with high nitrate concentration are mainly distributed around the northern and southern towns, and the distribution of ammonia nitrogen samples with high concentration is scattered. Atmospheric precipitation was the primary source of surface water and groundwater recharge in the region. The chemical characteristics of surface water and groundwater were mainly controlled by silicate and evaporite weathering, and were obviously affected by human activities. The surface water with extreme low concentration inorganic nitrogen was mainly from atmospheric precipitation, while the groundwater with the relatively high concentration inorganic nitrogen was mainly from domestic sewage and feces in agricultural areas. The mutual transformation of inorganic nitrogen components was affected by the redox conditions. The inorganic nitrogen of the pollution source in the surface layer was mainly ammonia nitrogen, and the concentration of ammonia nitrogen in groundwater is high. The nitrate was gradually enriched by nitrification accompanied with the downward migration of atmospheric precipitation. Our results are of great significance for understanding the causes and migration and transformation mechanism of inorganic nitrogen enrichment in groundwater in agricultural areas with dense water network, which is of great significance to the prevention and control of groundwater pollution in Jianghan Plain.