The error and timeliness of DEM may cause deviation from the actual situation in the extraction of hydrographic net; therefore, we proposed a method that combining the remote sensing information and DEM to extract hydrographic net. This method uses remote sensing image to extract the main stream of the drainages based on NDWI and spectral analysis, and the way of mathematical morphology is employed to remove the noise and refinement of the proposed binary graph. Based on the DEM extraction of river network, the water area threshold of the river net is determined by the relationship between the water area threshold and the density of the river network, and the pseudo-channel is eliminated rationally. Remote sensing system and DEM main water system channel correction control points should be set based on both results. The control points in the DEM water system layer should be rectificated with the RS main water system channel, so as to complete the DEM water system location and correction of planar waters.