The influence of foundation conditions on the dynamic response of suspended liquid storage structures in lead-based reactors is critical for seismic adaptability analysis owing to their unique configurations. Using a certain lead-based reactor as the research object, a fluid-solid coupling interaction model between the suspended liquid storage structure and the foundation was established using ANSYS, incorporating a viscoelastic artificial boundary to dissipate scattered wave energy and utilizing user programmable features (UPFs) for secondary development. The seismic response characteristics of the suspended liquid storage structure under different foundation conditions were systematically investigated. Results demonstrate that soft foundations considerably amplify the sloshing wave height of the internal liquid, while acceleration responses in horizontal and vertical directions are notably affected by foundation types. However, the variation trend and amplitude of overall displacement remain substantially stable. These findings provide technical references for the seismic design of lead-based reactors.