This paper briefly is based on the discussion of three fundamental characteristics of the ground (elevation accuracy, validity of elevation order, and the preservation of elevation features) and the concept of the model, then analyses major theoretical and practical shortcomings of the DEM generated in the mechanical model in depth, finally we proposes and discusses objects for feature modeling and the way of digital generalization, and discusses the principle of DEM digital generalization. We also give the 1:5 0000 and 1:1 0000 two series of DEM generalization maps, which achieve the desired results. Experimental results clearly show that: Only with digital generalization based on reliable DEMs which have expressed all terrain features, we can express DEM of required terrain feature on designated resolutions. That is no generalizing, there will be no DEM. The excellent consistency of Theoretical analysis and experimental results, makes this paper believe that objects for feature modeling and digital generalization will bring qualitative change to DEM, and will be a promising new way to solve hundred-year problem -combination and generalization of contours and water portfolio.