Abstract: Dongjiang Lake is a critical drinking water source in Hunan Province. The total phosphorus and ammonia nitrogen concentrations in Dongjiang Lake are rising, which causes that the water quality is on the critical line of cross-decline. However, the surface source pollution of Dongjiang Lake has a complex pathway into the lake. The existing water quality monitoring sections are not able to comprehensively reflect the water quality status of all rivers entering the lake. In this study, a surface source pollution model was developed based on the SWAT model. The model was used to identify the sources of pollution and to estimate the loads of surface source pollution in the basin. The reduction rate of different measures was also evaluated. The simulation results showed that the high loads nitrogen and phosphorus was located in the eastern part of the basin and the Guangqiao River, Tianzhuang River and Changwu River. The low loads of pollution was located in the middle part of the basin. The pollution source in the basin was dominated by urban life and agricultural fertilization. Based on the in-depth investigation of the current situation of surface source pollution management in the Dongjiang Lake watershed, specific reduction measures were proposed nted for urban living and agricultural fertilization pollution. The effects of these measures were evaluated in the model. The simulation results showed that the effects of the five management measures were, in a descending order, stubble mulching > contour farming > livestock farming > reduction of fertilizer application > urban life. A comparison with the actual water quality changes proved that the established model was applicable to the simulation of pollution reduction measures in Dongjiang Lake Basin. However, it should be noted that the risk of endogenous pollution still existed in the inlet of Dongjiang Lake. This study aimed to provide theoretical basis and data support for the control of exogenous nitrogen and phosphorus inputs towards a better management of water quality of the basin.