Land subsidence is a global phenomenon caused by a variety of factors and there are still many challenges in land subsidence monitoring.This paper presents the results upon the investigation of land subsidence with the combination of distributed fiber optics sensing(DFOS)technologies and microstructure analysis of soil.Two DFOS technologies including Brillouin optical time domain reflectometry(BOTDR)and fiber Bragg grating(FBG)were applied in two boreholes(namely GM03 and SZ01)in Su-Xi-Chang area,China,to monitor the movement of strata along the full borehole and the pore pressure in certain specific strata.According to the BOTDR monitoring results,the annual amounts of land subsidence in GM03 and SZ01 were~1.2mm and~2.9mm,respectively and the movement history of strata were clearly identified.For both boreholes,the main contributors of subsidence were the two aquitards(Ad2 and Ad3)adjacent to the second aquifer(Af2).Results obtained by FBG-based sensors showed good agreement with BOTDR and it confirmed that the deformation of aquifer was greatly controlled by pore pressure.