The purpose of this study is to develop WQMS(Water Quality Management System), which performs calculating pollutant discharge and forecasting water quality with water pollution model. Operational water quality management requires not only controlling pollutant but acquiring and managing exact information. ArcView was used to input or edit geographic data and attribute data, and Map Object was used to customize user interface. WQMS consisted of Database Subsystem & Model Subsystem. Database Subsystem consisted of watershed data from digital map, remote sensing image, government reports, census data and so on. Model Subsystem consisted of NSPLM (NonStorm Pollutant Load Model)-SPLM(Storm Pollutant Load Model). It calculates the amount of pollutant and predicts water quality. This two subsystem was connected through graphic display module. This system has been calibrated and verified by application to Mokhyun stream watershed.