Abstract This paper focuses the quantitative evaluation of non point sources of pollution by graphical maps of watershed and estimating area based load of pollutants of various land uses with the use of Arc/View Geographic Information System. The representative study is carried out in the Xinshan sub-watershed of Taihu watershed. It involves the simulation of pollutants load by watershed; watershed area and event mean concentration (EMC) by pollutants. Further the NPSP evaluation is carried out with the provision of Best Management Practice (BMP's) scenario in the watershed. BMP's utilization practice has provided the most efficient, practical and cost effective steps for the reduction of NPSP in the watershed. Using watershed boundary and land use data, nutrient EMC, and point Load, NPSP is evaluated based on PLOAD GIS model extension of Watershed 3.0. Model simulation is evaluated using tabular and graphical analysis. Support for this work is provided in the part by funding from the Natural Science Foundation in China for the project No. 50239030