Abstract: This paper established an evaluation system for nonpoint source pollution integrated Visual Basic with Map Info geographical information syseml(GIS)MapX and simulated BOD loads on annual average in the Yanjiang watershed in Zhejiang province in the case study. This study analyzed the application of GIS to nonpoint source pollution evaluation at the aspects of system frame and run process including data input,model parameters extraction,result visualization. This study indicated that integrating GIS technology with evaluation for nonpoint source pollution in watershed is effective in acquiring model parameters and enhancing the definition of data and evaluation result. It provided an effective method for nonpoint source pollution control in watershed.