D-InSAR technique has been increasingly used in the measurement of surface displacement over the last two decades. The incredible characteristics of D-InSAR technique are its high measurement accuracy in the order of centimeters, even millimeters; large spatial coverage and continuous monitoring capabilities in all weather and all time in monitoring and measurement of surface deformation due to earthquake, glacier dynamics, volcanic activities, ground subsidence, etc. This paper overviews the theory, method and application of D-InSAR techniques. Then three D-InSAR methods and related data processing flow charts are illustrated. A case study, which uses ENVISAT ASAR data as an example to perform 3-pass D-InSAR technique to generate coseismic deformation of L'Aquila earthquake is described. The data processing steps have been tested using Delft object-oriented Interferometric InSAR processing software. It is discussed in the end of paper that decorrelation effects both in spatial and temporal, as well as topographic factors, would hamper the quality of D-InSAR results.