Tianjin is one of the cities in the north of China where the land subsidence has most seriously developed. The land subsidence has been lasting for 50 years. In the paper, we use permanent scatterers interferometric synthetic aperture radar (PS-InSAR) technique to detect and measure ground movement in this area. The time serial measured results demonstrate that land subsidence in the study area, is controlled by geological tectonics, especially in south deformation areas. The detail information of deformation shows that the tendency and spatial extent of subsidence is controlled by geologic structures. Comparing the subsidence extracted by PS-InSAR technique to the leveling survey, both of them are mostly consistent. Meanwhile, it is revealled that different aquifers make different contributions to land subsidence. At last, we should take measures including set limit to groundwater exploitation, save water, and replenish groundwater artificially, also some new techniques (eg,InSAR) in measuring ground deformation are used to prevent and slow the land subsidence.