Taking the YD002 borehole in Tongzhou Bay area of Jiangsu Province as the research object, this paper establishes a DFOS (distributed fiber optic sensing) system of land subsidence to monitor the deformation and subsidence of Quaternary sedimentary layer in this area for a long time. Based on the monitoring data, the current situation and trend of land subsidence in this area are studied and analyzed. The results show that the main deformation source in this area is the compression deformation of the soil layer caused by the vertical water release of the confined aquifer group in the upper part of the main pumping layer. The whole stratum shows a compression trend, and the deformation of each compression layer is closely related to the variation law of groundwater level. Compared with the traditional layer-wise mark, the DFOS technology can more finely measure the vertical compression and rebound deformation of soil layer.