Abstract: A study on the interaction between the prestressed egg-shaped digester and liquid is performed in the paper. Through the computer program ANSYS, seismic evaluation of the digester is performed using a 3D finite-element model that includes the effect of fluid-solid interaction. The influence of coupling interaction on dynamic characteristic is analyzed. Natural frequencies, mode shapes, static response and dynamic response including the response acceleration, response displacement and response stress were calculated. Comparisons of calculated responses and those of shaking table tests for the first time in China show reasonably good agreement. It demonstrates that this finite-element model is reasonable and can be applied to the engineering design.