Proceeding of the Joint International Symposium on Deformatuon Monitoring. 2-4 November, 2011. Hong Kong. China. Report. Land subsidence is a severe hazard that will threat the safety of local people and urban infrastructure. Beijing and Tianjin areas have been suffering from land subsidence which is supposed to be induced by over-exploitation of ground water. The project of Beijing-Tianjin inter-city high-speed railway finished in 2008 plays an important role in the two major cities of China. It is well known that a tiny deformation of the rail will cause serious consequences. So to maintain the safety operation of the high-speed railway, the continuous monitoring of land subsidence along high-speed railway is very important. InSAR time series techniques such as Persistent Scatterer Interferometry (PSI) and Small Baseline Subset (SBAS) can overcome the limitation of geometrical and temporal decorrelation and atmospheric phase, thus it can successfully detect ground displacements to a degree of accuracy comparable to traditional geodetic technique such as leveling. In this paper, a total of 9 TerraSAR-X stripmap scenes between February 2011 and August 2011, acquired over the Beijing areas have been used to monitoring the land subsidence along the Beijing-Tianjin inter-city high-speed railway. SBAS approach is applied to extract linear deformation velocity information with the reduced set of SAR data. The improved identification method of stable coherent points using multi-threshold is explored and the Delauney triangulation is applied to establish connections among the selected points. After phase unwrapping process, the linear deformation rate is obtained from the time series with a least square fashion. The preliminary experimental results show that with the high resolution TerraSAR-X images the dense PS can be identified and the rapid land subsidence can be detected. The monitoring result is important for predicting potential hazards and designing compensation strategies. TerraSAR-X interferometry can be a remarkable potential technique to monitoring of land subsidence related to man-made linear features such as high-speed railway.