Abstract: This study took the Poyang Lake Region as the research area and the shallow groundwater was selected as the research object. The distribution characteristics and temporal and spatial variation of nitrate in shallow groundwater in the Poyang Lake Region were studied and source of nitrate in groundwater was analyzed. Nitrate concentration in shallow groundwater was between 0.5-21.6 mg/L with an average of 7.0 mg/L. In the wet and dry seasons,nitrate concentration was 0.7-21.6 mg/L and 0.5-15.7 mg/L, respectively. Groundwater with high concentration of nitrate was mainly found in the typical agricultural irrigation area. The hydrogen and oxygen isotopic characteristics of water samples showed that surface water was mainly from meteoric precipitation, and influenced by other recharge sources and evaporation. Shallow groundwater was mainly recharged by local meteoric precipitation and was mixed with surface water, less affected by evaporation. The results of nitrogen and oxygen isotopic composition of nitrate showed rainfall, irrigation activities, land use type and fertilizer application were major factors affecting the concentration and distribution of nitrate in shallow groundwater in the study area. The calculation results using Bayesian model showed that soil nitrogen had the maximum contribution rate to nitrate in groundwater, with an average contribution rate of 44.6%. Atmospheric precipitation had a secondary contribution rateto nitrate in groundwater with an average contribution rate of 28.2%. The contribution rates of nitrogen fertilizer, sewage and feces were 19.4% and 7.8%, respectively.