In order to overcome the limitation of cross correlation coregistration method for Synthetic Aperture Radar(SAR) interferometric pairs with low coherence,a new image coregistration algorithm based on Fringe Definition Detection(FDD) is presented in this paper.The Fourier transformation was utilized to obtain spectrum characteristics of interferometric fringes.The ratio between spectrum mean and peak was proposed as the evaluation index for identifying homologous pixels from interferometric images.The satellites ERS-1/2 C-band SAR acquisitions covering the Yangtze River plain delta,eastern China and ALOS/PALSAR L-band images over the Longmen Shan mountainous area,southwestern China were respectively employed in the experiment to validate the proposed coregistration method.The testing results suggested that the derived Digital Elevation Model(DEM) from FDD method had good agreement with that from the cross correlation method as well as the reference DEM at high coherence area.However,The FDD method achieved a totally improved topographic mapping accuracy by 24 percent in comparison to the cross correlation method.The FDD method also showed better robustness and achieved relatively higher performance for SAR image coregistration in mountainous areas with low coherence. In order to overcome the limitation of cross correlation coregistration method for synthetic aperture Radar (SAR) interferometric pairs with low coherence, a new image coregistration algorithm based on Fringe Definition Detection (FDD) is presented in this paper.The Fourier transformation was utilized to obtain spectrum characteristics of interferometric fringes. ratio ratio spectrum mean and peak was proposed as the evaluation index for identifying homologous pixels from interferometric images. satellites ERS-1/2 C-band SAR acquisitions covering the Yangtze River Plain delta, eastern China and ALOS / PALSAR L-band images over the Longmen Shan mountainous area, southwestern China were respectively employed employed in the experiment to validate the proposed core method. The testing results suggested that the derived Digital Elevation Model (DEM) from FDD method had good agreement with that from the cross correlation method as well as the reference DEM at high coherence area FDD method achieved a totally improved topographic mapping accuracy by 24 percent in comparison to the cross correlation method. FDD method also showed better robustness and achieved relatively higher performance for SAR image coregistration in mountainous areas with low coherence.