The SAR Interferometry technique is an effective method for monitoring ground deformation and has been used widely. First of all, it has some advantages compared with the conventional approaches, such as covering large area, high spatial resolution and low cost. However, its accuracy and robust are reduced for atmosphere and land cover conditions. In recent years, the Permanent Scatterers technique has been developed, which can reduce the spatial and temporal decorrelation by using a time series of SAR images. At present, it has been used in monitoring landslide, subsidence and geological disaster widely. PS technique has more accuracy, higher temporal resolution and utilization efficiency compared with traditional DInSAR. However，with this technique some limitations should be noticed. For example, only small areas (less than 5 km×5 km large) could be processed, where there were too many images and only slow surface deformation phenomena could be detected. In recent years, some new approaches have been presented such as using corner reflectors, multi-plat PS technique and coherent pixel technique for improving PS technique. 