To study non-point source pollution carried by rainfall runoff in the large-scale basins, based on semi-distributed land use runoff processes (SLURP) model, the construction method for prediction models of total phosphorus (TP) and total nitrogen (TN) load, and the future meteorological parameters and land-use map were proposed respectively. By application of the proposed approaches, the monthly TP and TN loads of land use, livestock and agricultural population on the Jialing River watershed in the future were simulated and analyzed. The results showed that the increased volume of rainfall runoff, livestock and poultry in predicting year led to increased pollution load. Compared with the base year, the monthly maximum increases of nitrogen and phosphorus load were both in June, which were 28.6% and 22.5% respectively. The total land-use output load changed little together with changes of land-use types due to measures such as returning farmland to forests, but it was still the largest contribution.