Abstract: The water circulation filter in the containment of nuclear power plant must ensure complete functionality subjected to earthquake. To perform seismic analysis of filters submerged in water, the additional mass effect caused by fluid-structure interaction (FSI) should be considered. Underwater shaking table tests were conducted to study the variation of the fundamental vibration frequency of the filter and analyze the influence of white noise vibration amplitude, water depth, filter bending angle, porosity, and the spacing between fin units on the fundamental vibration frequency of the filter. The experimental results indicate that the FSI between the water and the filter is significant and it greatly reduces the overall fundamental vibration frequency of the filter. As the water depth increases, the fundamental vibration frequency of the filter decreases linearly. Once the filter is submerged, the fundamental vibration frequency stabilizes, with the standard fin unit and fin group exhibiting a reduction to 48% of the dry-state frequency, and the additional mass ratio relative to the overall filter structure mass reaching 3.28. The intermediate plate in the fin unit makes the effect of porosity on the fundamental vibration frequency insignificant. When the intermediate plate is removed, an increase in porosity reduces the FSI effect, leading to an increase in the structural fundamental vibration frequency. The spacing between the filter fin units has no significant effect on the fundamental vibration frequency or the additional mass of the filter fin group.