The Geographic Information System (GIS) has the strong abilities of spatial data analysis and visualization.It can reflect the spatial distribution of the non point source pollution.Integrating GIS with the non point source pollution model can greatly reduce the difficulty of non point source pollution modeling.The current situation of non point source pollution study in China and abroad is summarized.Combing the BASINS system and the PLOAD model developed by USEPA,the application of GIS in the study of non point source pollution in watersheds is analyzed from the three aspects of data input, parameter extraction and result visualization,and is simulated at the Yanjiang watershed in Zhejiang province as a case study.This analysis could provide some use for reference in this field.