Abstract: Jianshanying bridge is a control station on the newly-built high-speed railway line from Guiyang to Guangzhou. This paper combined the methods of field geological survey, field monitoring, drilling, geophysical exploration and laboratory test to analyze the main reasons for the abnormal lifting of the great bridge piers. The geological structure distribution in the study area was obtained by geological mapping and drilling core development. The developmental state of groundwater in the bridge site is deduced from the survey of surface water and audio magnetotelluric exploration (AMT). Indoor expansion tests of drill core were carried out to study the water-absorbing expansion characteristics of the foundation rock soil in the bridge site area. The results show that excluding the reasons of geological structure and groundwater in the confined aquifer, the superstructure rises and falls due to the physical and chemical reaction between expansive rock mass and groundwater. The Permian Wujiaping formation (P2w) in the bridge site area has the potential swelling force estimated to be between 3 MPa and 59 MPa, which is much greater than the structural loads (ranging from 1.38 MPa to 13.5 MPa). Under the action of axial pressure of 1.05 MPa, the undisturbed expansive rock sample absorbs water and has an expansion strain of 0.35%. Combined with the existing studies, it is found that the expansion formation 130 m thick can cause the uplift of the superstructure of 45.5 mm. Therefore, the Permian Wujiaping formation (P2w) is mainly responsible for the abnormal rise and fall of the bridge piers due to its water absorption expansion and water loss shrinkage, combined with groundwater recharge and discharge.