Watershed boundary and stream network can be extracted from DEM(Digital Elevation Model) using GIS software such as ARC/INFO or ArcView Spatial Analyst. However, there exist many errors in the generated watershed boundary and stream network just by operating sink removal function of the present software. This paper present the error reducing method to delineate watershed boundary and generate stream network especially in plane areas by using stream burning techniques known as Fillburn and Agree bum. These preprocessing techniques of DEM dramatically decreased the errors comparing with the results by no-bum DEM.