Abstract: Numerous pumped storage power stations are currently in the planning and construction phases.Owing to environmental protection requirements, substantial waste slag accumulates on dam slopes of rockfill dams, forming slope-compaction zones as referred in below context.The absence of specific standards for this zone leads to the application of general dam body standards for assessing seismic safety, often resulting in over-design and economic inefficiency, particularly in regions prone to severe earthquakes.Therefore, it is of considerable engineering significance to investigate influence mechanisms and evaluation methodologies of the slope-compaction zone under strong seismic conditions.Considering dam-foundation interactions, analyses such as elastoplastic dynamic response, equivalent-linear analysis, and time history stability assessment are conducted for a rockfill dam located in an area susceptible to extremely strong earthquakes.The impact of the slope-compaction zone on the integrity of the dam is investigated, and a method for evaluating its seismic safety is proposed.Findings reveal that the normal pressure exerted by the slope-compaction zone on the dam′s slope significantly exceeds the shear forces along the slope, thereby aiding in reducing seismic deformation of the dam structure.Moreover, the porosity of the slope-compaction zone does not influence seismic deformation, suggesting that enhancements to construction standards in this zone are unnecessary.The minimal safety factor for the dynamic stability of the slope-compaction zone only refers to a superficial, non-threatening sliding surface that does not threaten the dam′s safety.It is recommended that either the overall deformation of the dam or the stability (safety factor and slip deformation) of critical sliding surfaces through the dam body be used to assess the seismic safety of the slope-compaction zone.The research provides support for the seismic design and safety evaluation of rockfill dams with a slope-compaction zone in areas prone to strong earthquakes.