Abstract: The agricultural non-point source (ANPS) is the most important factor for water environmental deterioration and lake eutrophication. Based on AnnAGNPS (Annualized Agricultural Non-point Source) model, the output loading of nitrogen and phosphorus from Qiandao Lake watershed was predicted, and the characteristics of spatial-temporal distribution of nitrogen and phosphorus were discussed. The study showed that the predicted results coincided with measured results, which suggested that this model be suitable for prediction and assessment of pollution loading of ANPS.