Hydrological modelling of surface runoff for Lake Poyang watershed is of significant importance since the surface runoff is the main source of water inflows of the lake. The hydrological model can be used to reveal the influences of changes of natural and human conditions in the watershed on the surface runoff and consequently on the water balance of the lake. Hydrological modeling of the Lake Poyang watershed is challenging due to the complexities of the system, e.g. the large size (162.2 ×10⁴ Km²) of the area with high heterogeneity of soil types and land uses, contribution of stream flow from multiple rivers to the lake, and the overland flow at lake-side zone. Relevant methods to simulate the above features were presented and a distributed hydrological model was developed in this paper for Lake Poyang watershed. The model was well calibrated and validated against the observed daily stream flows at six stations from 1991 to 2001. The results were satisfactory inthe general model predictions, with high monthly efficiencies of 0.82-0.95 for Ganjiang, Xinjiang and Raohe rivers. Accuracy of model prediction for Fuhe and Xiushui rivers was slightly lower, with efficiencies ranging from 0.65 to 0.78. The model indicated that the average volume of annual surface runoff to the lake for the simulation period was 162.3 billion m³, of which Ganjiang, Xinjiang and Fuhe rivers contributed 47%, 13% and 12%, respectively. Direct overland flow to the lake at the lake-side zone accounted for about 4%. The rest (24%) was contributed via Raohe, Xiushui rivers and several tributaries. The model successfully simulated the hydrological processes of Lake Poyang watershed, and can be used to evaluate impacts of human activities on water variability and water balance of Lake Poyang.