Abstract: In order to accurately identify the spatial distribution and sources of groundwater nitrate pollution in Xuanhua District of Zhangjiakou City, according to the groundwater quality monitoring data of both sides of the Yanghe River in Xuanhua District, Zhangjiakou City, hydrochemical analysis method was used to analyze the status of nitrate pollution, and nitrogen and oxygen stable isotope method was used to qualitatively analyze the sources of pollutants. The ArcGIS software was used to visualize the nitrate concentration and nitrogen and oxygen isotope characteristic values of groundwater, and more intuitively show the temporal and spatial differences of groundwater environmental quality. The contribution rate of each pollutant was quantitatively calculated according to SIAR model (isotope mixing model). The results show that: (1) In Xuanhua District of Zhangjiakou City, nitrate nitrogen was the main pollutant of groundwater, with an average concentration of 27.23 mg/L. The high pollution concentration occurred in construction land. (2) The isotopic characteristic values of typical pollutants in the study area were as follows: δ¹⁵N-NO₃^- in soil was from 1.46‰ to 7.71‰, and δ¹⁵N-NO₃^- in feces and sewage ranged from 9.49‰ to 17.57‰, which can be used to enrich the distribution database of δ¹⁵N-NO₃^- characteristic values. (3) Nitrate pollution mainly came from soil nitrogen, feces and sewage. The characteristics of water chemistry and isotopes showed that nitrification was the main process of nitrogen migration and transformation. (4) The results of SIAR model showed that the contribution rates of soil nitrogen, feces, Inorganic fertilizer and industrial waste water were 44.36%, 43.35% and 9.24%, respectively. The study shows that nitrate pollution is mainly affected by domestic sewage, industrial production activities and agricultural irrigation in this area, the pollutants mainly come from soil nitrogen, feces and sewage, and the pollution of construction land is more serious than that of cultivated land.