Abstract: Aiming at the abnormal vibration problem of the aqueduct pier in the transition section of the long-distance open channel under the condition of severe fluctuation of water flow, taking the Shierlihe aqueduct in the Middle Route of South-to-North Water Diversion Project as an example, the operation process of prototype sluice gate was reproduced by a physical model test with a length scale of 1∶36,and the hydrodynamic factors closely related to the pier vibration were analyzed.The vibration mechanism of the middle pier was deeply discussed from the aspects of the length and shape of the inlet and outlet piers, the arrangement of the transition section and the operation of the gate.The results showed that the pier vibration was mainly caused by the lateral oscillation of the water flow impacting the building and the intermittent free horseshoe vortex state occurring at the end of the separation pier.The water level fluctuation and pier vibration intensity of the aqueduct section can be effectively reduced by optimizing the layout of the middle pier, adjusting the contraction angle or diffusion angle of the inlet and outlet transition section and sluice operation mode.The research results can provide reference for the design and operation of large-scale water diversion project aqueduct.