Abstract: For engineering applications, a variety of simplified analysis models and calculation methods considering the hydrodynamic force have been proposed based on the assumption of incompressible water. Some typical methods include the rigid-structure method, Morison method and a method based on approximation of fundamental-frequency. The seismic responses of elastic cantilever circular piers excited by horizontal earthquake were analyzed to study the difference caused by the above methods. By using 3 ground motion records on soft soil site and selecting a series of depth and wide-depth ratio as parameters, 144 cases of bridge piers were considered. The horizontal displacement at the top of the piers, shearing force and bending moment at the bottom were compared with the exact solutions based on the radiation theory of incompressible water. Then, the range, mean values and coefficient of variation of the relative errors of the peak values of responses were presented. Based on the analysis of errors, calculation accuracy of the simplified methods was investigated and the applicable scope was given preliminarily.