Abstract: The randomness of seismic motion significantly affects the dynamic response of dams. As a critical component of dam seismic safety, the assessment process should also thoroughly consider the influence of load randomness. This paper is based on a large number of random dynamic finite element calculations for high earth and rockfill dams. It explored the relationship between the dam crest settlement rate and the cumulative sliding displacement, two important deformation indicators of the dam. Additionally, it proposed safety control standards for earth and rockfill dams and the Probabilistic Density Evolution Method was used to analyze the ultimate seismic resistance of them. The results indicate that the settlement rate increases with the cumulative sliding displacement and follows a logistic growth model. Taking 10% exceedance probability as an example, the ultimate seismic resistances for a 250m regular high faced rockfill dam and a high-core rockfill dam are approximately 0.7g ~ 0.75g and 0.8g ~ 0.85g, respectively. A new probabilistic approach is proposed for evaluating the ultimate seismic resistance of dams.