<p>Groundwater nitrate pollution poses a critical threat to karst water resources in the Xiaoli area of Jinan. Based on the water chemical data of 23 samples, this study employed integrated techniques including hydrochemical analysis, reverse hydrogeochemical modeling, and the absolute principal component score-multivariate linear regression (APCS-MLR) model to reveal pollution characteristics and sources. The research found that groundwater chemistry type was mainly HCO₃-Ca·Mg type, with its evolution primarily controlled by rock weathering and overlaid by human activities. At the same time, reverse hydrogeochemical modeling demonstrated the influence of biogeochemical processes (nitrification). The nitrate exceedance rate was 48% and the pollution was spatially distributed in a northeast-southwest direction, mainly concentrated in the runoff area and discharge area, with particularly severe contamination near towns. Source apportionment identified agricultural activities such as fertilization and irrigation as the primary contributors to nitrate pollution, accounting for 62.35%, followed by the discharge of domestic sewage and feces, accounting for 20.20%. To ensure groundwater safety in the study area, strict control of agricultural fertilizer application is essential, alongside monitoring the discharge of domestic sewage and feces, and conducting regular groundwater quality monitoring. These findings provide a basis for groundwater nitrate pollution prevention and control in the study area and other similar regions.</p>