[Objective] Concerning the shortage in the extraction of plain river network based on DEM, we adopted a new method to extract plain river network and to provide basis for automatic drainage extraction method.[Methods] Using Acr Hydro Tools and SWAT, the river network of Yaojiang river basin in Ningbo City was extracted in DEMs with different contour. The extracted total area of the basin and total length of rivers were used as the main index of quantitative analysis. Relative error formula, matching error formula of river network and Visual Similarity Duplicate Image Finder software were used for comprehensive evaluation and error analysis.[Results] With the help of the real river network, the extracted results based on Neat DEM by Acr Hydro Tools and SWAT were very bad. However, the extracted river network, basin and total basin export based on Adjacent DEM were consistent with the actual, and the precision and similarity were also high.[Conclusion] Extracting basin and river network with Acr Hydro Tools and SWAT are all desirable, but the SWAT is more convenient. The quality of river network extraction is dependent on DEM contour and also dependent on whether the DEM is tangent with the total basin export or not.