Abstract: To evaluate the effectiveness of comprehensive control measures for total nitrogen (TN) pollution in the Oujiang River Basin and to reveal its driving mechanisms, a hydrological-water quality model of the basin was constructed based on the SWAT model. Methods such as hierarchical cluster analysis, statistical analysis, correlation analysis, and principal component analysis were comprehensively applied to systematically reveal the spatiotemporal distribution characteristics of TN load and TN load intensity, identify major risk source areas, and quantitatively assess integrated management measures as well as the correlation between TN pollution and economic indicators through scenario simulations. The results show that:(1) Model verification demonstrated that the SWAT model performs well in the basin, with all evaluation indices (R² > 0.6, NSE > 0.6, |PBIAS| < 0.3) meeting accuracy requirements during both the calibration and validation periods.(2) Spatiotemporal analysis revealed significant differentiation in TN load: spatially, a pattern of “downstream > upstream > midstream” was observed; temporally, the wet-season load accounted for more than 74% of the annual total, highlighting the hydrologically driven seasonal pattern. Using a comprehensive risk index method, the Songyinxi sub-basin, the main Oujiang River section, and the Nanxijiang sub-basin were identified as key source areas, which contributed 41.5% of the TN load while occupying 37.83% of the basin area.(3) Based on hierarchical cluster analysis, the basin was divided into three pollution-type zones. A corresponding “zoning-based systematic scheme” achieved a 60.71% reduction in TN load, significantly outperforming individual measures (12.22%–42.46%).(4) Combined with driving-factor analysis, TN pollution in the Oujiang River Basin was closely coupled with urbanization and economic growth. The main driving forces were comprehensive socio-economic activities centered on urban expansion, population agglomeration, and industrial/service-sector development.The findings provide a scientific basis for formulating systematic TN reduction strategies that account for spatial heterogeneity and for promoting coordinated regulation incorporating economic indicators in the Oujiang River Basin.