Channel networks are important features for describing the topography of drainage basins. With the progress of GIS and more accessible digital elevation modeling (DEM) data, we can now extract the channel network from DEM readily. Using the GIS function called flow accumulation from grid-based DEM is the most popular method on extracting the channel network. However, the threshold of flow accumulation is the key factor in channel network extraction and should be decided more accurately. This study extracts the channel network of the Chi-Cha-Wanwatershed from 40 meters resolution DEM with the integration of constant drop law, GIS and statistical methods, and compares it with the digital data from 1:10,000 and1: 25,000 topographic maps. The results show that channel networks extracted from DEM match Horton’s laws with a high level of accuracy, but could not prove that the threshold of flow accumulation found by constant drop procedures is the optimal result. The frequency distribution of the channel lengths of first-order segments skewed to the right, and should be corrected by using the logarithm of length when using the constant drop procedure. The parameters of Horton’s laws measured from extracted channel networks are sensitive to the changing threshold. The comparison of spatial accuracy between the extracted channels and the rivers shown on the topographic maps demonstrates some limitation of flow the accumulation method of which, the identification of first-order channel heads is the major one.