Abstract: Large-tonnage prestressed pier of a hydropower station is applied to resist huge hydraulic thrust from the radial gate arms. Pier cable tension monitoring in nearly two years shows that part of the anchor tensile force had lost by more than 15% and not converged, and that the pier had strong vibration during the flood discharge. In order to clarify the influence of the anchor cable force losses on dynamic characteristics of the pier(including modal characteristic, dynamic displacement and dynamic stresses), a finite element overall model of pier-foundation- anchor is established, and the pier hydraulic model measuring the overall surface loads acting on the pier surface is set up to obtain the overall hydrodynamic loads under different operating conditions. Then, the overall surface loads are taken as the input loads for calculation of pier dynamic response, and analysis of the influence of primary and secondary anchor cable force losses on the pier dynamic characteristics is made. Those research results can provide an important reference for the safe operation of the same projects.