Total load control of riverine pollutant transport is critical for safeguarding water environmental quality, particularly under the background of frequent extreme precipitation and intensified hydrological variability, where the relative changes between pollutant loads and discharge directly determine the ultimate concentration levels in rivers. Elucidating the response characteristics of concentration and flux to discharge variations is of great significance for watershed water quality risk assessment. Based on daily monitoring data from 136 representative stations across China""s major river basins during 2021–2024, combined with synchronous hydrological records, this study analyzed the spatiotemporal heterogeneity of total nitrogen (TN) and total phosphorus (TP) concentrations and fluxes, and employed power function regression models to establish concentration-discharge (C-Q) and flux-discharge (F-Q) relationships to decipher their response mechanisms to discharge variations. The results revealed significant spatial inconsistency between concentrations and fluxes of nitrogen and phosphorus in Chinese rivers. Northern basins exhibited a "high concentration-low flux" pattern, with TN concentrations typically sustained between 4.0 and 8.0 mg/L and an average TP concentration of 0.093 mg/L, yet transport fluxes remained low due to limited runoff; conversely, southern basins displayed a "low concentration-high flux" pattern, with average TN and TP fluxes (4.29 kg/km2/d and 0.18 kg/km2/d) significantly exceeding those in the north (3.62 kg/km2/d and 0.12 kg/km2/d). Seasonal fluctuations revealed fundamentally distinct driving mechanisms for nitrogen and phosphorus: TN, predominantly in dissolved form, was governed by dilution effects, exhibiting "high concentration during dry season and high flux during wet season" characteristics, with runoff being the decisive factor for flux variation; TP, primarily in particulate form, was dominated by scouring effects, where intense rainfall during the wet season triggered soil erosion and sediment resuspension, causing concentration and flux to peak synchronously. C-Q analysis indicated that TN concentration was significantly negatively correlated with discharge (northern b = -0.20, southern b = -0.16), dominated by dilution effects, while the relationship between TP concentration and discharge was weak, particularly failing to reach significance in northern basins. F-Q analysis showed no significant regional difference in TN flux sensitivity to discharge, whereas TP flux sensitivity was significantly higher in the north (b"" = 0.41) than in the south (b"" = 0.28), indicating elevated phosphorus export risk in northern basins during extreme rainfall events. In conclusion, region-specific management strategies are recommended: northern basins should prioritize dry-season concentration control and rainy-season particulate phosphorus export prevention, while southern basins should focus on wet-season total load control and early warning systems for concentration rebound risks during low-flow periods.