Abstract: The effect of hydrodynamic pressure should be considered in the seismic analysis of deep water bridges. The Morison equation is widely used to calculate the hydrodynamic pressure of bridge piers. It is evolved from the calculation formula of wave force. Its applicability to calculate the seismic hydrodynamic pressure has not been verified. There is also a lack of experimental research on the seismic hydrodynamic pressure of bridge piers. In this paper, a set of underwater shaking table test systems was designed. Shaking table tests with different cases were conducted on the bridge pier specimens of different sizes under sinusoidal excitation. The distribution law and changing law of the acceleration and hydrodynamic pressure of the piers were studied under different excitation amplitudes, excitation frequencies, section diameters and water depths. The experimental results of the hydrodynamic pressure and the calculated results by the Morison equation are compared to verify the applicability of the Morison equation under earthquake action. The results show that the influence of the excitation amplitude, excitation frequency, cross section diameter and water depth should be considered in calculating the acceleration and hydrodynamic pressure of piers under earthquakes. The Morison equation is not applicable to the calculation of hydrodynamic pressure of piers under earthquakes and should be modified based on many underwater shaking table tests.