Abstract: For the vibration problems of the outlet tower of the large-scale high lift pumping station in the operation process, the outlet tower of the 6th pumping station of the phaseⅡ main line of Jingtaichuan electrical irrigation district in Gansu Province was taken as a typical case study and its three dimensional finite element numerical simulation model was established using the software ANSYS. In its normal operating state, the subspace iteration method was used to identify its modal parameters based on natural excitation and obtain its first 6-order vibration modes, analyzing the vibration modal of the outlet tower. The analysis results show that the base frequency of the outlet tower is 9.91 Hz during the normal operation, and the main vibration direction is perpendicular to the normal direction of the pressure pipelines; and the vibration mode of the outlet tower is fundamentally in accordance with the roles of transverse-vertical-torsion, and mainly at the central hollow column. The numerical analysis results are in good agreement with the DASP-testing results, indicating that the simulation results of the subspace iteration method are valid and reliable. The research results can provide a theoretical basis for the renewal design of the outlet tower of the large-scale high lift pumping station, meanwhile give some technical references for the modal parameters’ identification of the hydraulic structures in the irrigation district.