Interferometric Synthetic Aperture Radar (InSAR) is a powerful instrument for large scale acquisition of height data for bare earth as well as for vegetated areas and artificial above-ground objects. For many applications, the generation of a bald earth digital elevation model (DEM) is also required. This paper introduces the method of generating a bald earth DEM, referred to as the hierarchical surface fitting technique [7], which operates on the digital surface models (DSM) created using the X band InSAR data provided by the Institute of Electronic, Chinese Academe Sciences. After a short description of the algorithms, the paper presents the results of this technique applied to several DSM data sets, which are accomplished by VC++ program and show that this technique can remove artificial above-ground objects while retaining most of the detail of the original data.