AbstractHigh accuracy DEM (Digital Elevation Model) can be derived from SAR (Synthetic Aperture Radar) acquisitions by InSAR (Interferometric synthetic aperture radar) technique. The principle of InSAR is briefly introduced in this paper. And DEM measurements are compared with the 1:50,000 China DEM to validate the method. The good coherence between these two DEMs indicates that InSAR is potential in DEM measuring with low cost and high accuracy.In the second part of this paper, DEM derived with an external low-accuracy DEM (SRTM: Shuttle Radar Topographic Mapping) is compared with the one without an external DEM. The results show that the latter is more unstable than the former, besides it has an overall offset. DEM is significant topography information. With the launch of high accuracy SAR satellite, InSAR will provide a cost-effective way to produce DEM.