Decorrelation caused by temporal changes influences phase unwrapping of differential interferogram in repeat pass Differential SAR interfetometry（D-InSAR）.Phase delay due to atmosphere disturbance degrades the accuracy of D-InSAR for small deformation monitoring.In this paper

we present a Coherent Point Targets Interferometry approach to retrieval the phase history and estimate the linear deformation of a coherent scatterer.A multi-baseline interferograms algorithm based on discrete and temporarily natural or artificial reflectors is developed.In this algorithm

a multi-reference image strategy for interferograms generation is adopted to form the interferograms stack.A bi-threshold algorithm is used for coherent point targets identification.Those pixels preserving a good coherence level and presenting a point target character are identified from the whole set of interferograms.The phase regression model is used to estimate the linear deformation rate and DEM error of the coherent point targets. The method presents high flexibility with respect to the required number of images and baseline length.The technique has been tested with ENVISAT-ASAR data for land subsidence rate derivation of Cangzhou city.