The main objective of this study is to extract the hydro-geometric information of the Pyongchang River basin, headwaters of the South Han River. A GIS is capable of extracting various hydrological factors from DEM (digital elevation model). One of the important tasks for hydrological analysis is the division of a watershed. It can be an essential factor among various geometric characteristics of a watershed. In this study, the watershed itself and other geometric factors of a watershed are extracted from DEM by using a GIS technique. The manual process of tasks to obtain geometric characteristics of a watershed is automated by using the function of ArcInfo software as a GIS package. Scanned data is used for this study and it is converted to DEM data. Various forms of representations of spatial data are handled in the main modules and a GRID module of ArcInfo. A GRID module is used on a stream in order to define the watershed boundary, so it would be possible to obtain the watersheds. Also, a flow direction, stream networks, and others are generated. The results show that GIS can aid watershed management and research and surveillance. Also, the geometric characteristics as parameters of the watershed can be quantified by using a GIS technique. Reasonable results can be obtained as compared with conventional graphic methods.