This study analyzed the effects of reducing nutrients by managing pollution sources from cultivated area and livestock area in order to improve the water quality of the Lake Paldang Basin. To predict the effects of reducing nutrients in the Lake Paldang Basin, water pollution sources were first analyzed and possible scenarios to reduce the sources were selected accordingly. Using the basin environmental database, water flow rates, and TN and TP concentrations were simulated based on the Soil and Water Assessment Tool (SWAT) model. Model evaluation indices were calculated through the calibration and validation of water flow rates, and TN and TP concentrations, and they were found that simulation values reflected measurement values well, and that it was possible to evaluate the Lake Paldang Basin both qualitatively and quantitatively. In the case of Scenario 3 in which a measure to reduce pollution sources from both cultivated area and livestock area was applied together, the concentrations of TN and TP were reduced by 29.6% and 28.6% respectively. It is believed to be important to improve water quality by managing pollution sources from both cultivated area and livestock area particularly in area like the Lake Paldang Basin where agricultural and livestock production activities are actively conducted. The results of analyzing the effects of reducing nutrients in the Lake Paldang Basin showed that the concentrations of TN and TP were reduced to 3.42 mg/L and 0.167 mg/L respectively in Scenario 3. It was found that measures to reduce pollution sources from cultivated area and livestock area were effective for improving the water quality of the Lake Paldang Basin. It is also believed that reducing the amount of fertilizer applied to cultivated area is effective for managing nutrients, and that it is necessary to expand environmental infrastructure to reduce pollution sources from livestock area.