TerraSAR X-band (TSX) data can provide a high resolution of 1m, short revisit period of 11 days, and sensitive ground subsidence information. Permanent Scatterers (PS) technology was developed as a powerful tool for extracting the ground displacement information from TSX images. In this work, we exploit the potential of TSX for monitoring ground subsiding for the urban area in Hong Kong. A total of 57 TSX images and 11 TanDEM-X (TDX) images acquired between 25th October 2008 and 4th May 2012 were used in the InSAR time series analysis for retrieving subsidence in the study area. A Corner Reflector (CR) validation test is conducted in the area to quantitatively analyze the performance of PS analysis, and the result indicates that the analysis can achieve millimetric accuracy for its monitoring the ground subsidence.