DEM-based　drainage　extraction　is　a　hot　spot　in　digital　hydrology　research.　This　paper　has　analyzed　the　method　of　drainage　extraction　based　on　DEM,　used　Hydrology　tools　in　ArcGIS　software　to　build　the　model　of　drainage　extraction　and　published　the　model　to　geoprocessing　service.　Taking　Jiulong　River　basin　DEM　as　an　example,　this　paper　used　geoprocessing　service　to　realize　drainage　automatic　extraction　in　the　network　environment.　The　comparison　of　GP-based　drainage　extraction　and　actual　drainage　system　shows　that　using　this　GP-based　drainage　extraction　method　to　extract　Jiulong　river　basin　in　general　can　objectively　reflect　its　space　distribution