Any background for the topographic growth of any area includes two factors: climate and geology. The factor of climate is concerned with local geographic location which decides the kind of erosion, and affects the strength of erosion as well; as to the factor of geology is the base which reflects the growth of topography. Therefore, different topographies create different river networks that affect the generalization for map of river networks indirectly. Upon this point of view, this text intends to take the relief (altitude, slope and relative height) which is most aware of among the topographic features and to take the drainage basin as the topographic unit to make the geomorphological classification to discuss the relationship between topographic area and river networks generalization.