Synthetic Aperture Radar Interferometry (InSAR) is a new and potential technology that has been developed in the last decade or so for observation of the Earth. It can be used to generate large-area (even global) DEM or to detect Earth surface deformation by means of interferometric phase data and attitude data of the radar platform. In particular, Differential InSAR (D-InSAR) has been demonstrated to have unprecedented ability to measure and monitor Earth surface change with excellent characteristics of continuous spatial coverage and nearly automatic processing and high accuracy (up to cm-level or even better). This paper first introduces the basic principles of InSAR and D-InSAR, and summarizes the involved key processing algorithms of interferometric technology, including SAR images coregistration,
phase unwrapping and baseline estimationetc. Then, some factors, that affect the quality of interferometric products, are generally analyzed,i.e., phase quality and baseline parameters play very important roles on interferometric processes. Finally, emphasis is placed on reviewing D-InSAR applications in measuring and monitoring Earth surface deformations caused by earthquakes, post-seismic displacements, ground subsidence, landslides and volcanic movements.