This paper studies the dynamic behavior of a typical earth-dam using non-linear dynamic analysis under different earthquake records. One of the most important components in non- linear dynamic analysis of earth-dams is the evaluation of their stability considering the permanent displacement as a performance indicator. Varieties in acceleration time histories coupled with various geometry and heterogeneous material properties of the earth structures lead to diversity in non-linear responses under different real accelerograms. In this study, an equivalent harmonic load related to earthquake records with specific magnitude and frequency is defined and is applied to a 70m tall earth-dam during four real acceleration time histories. The induced-displacements were then measured under each real time record along with their defined harmonic loads at the dam crest. The resulting displacements and their harmonic equivalent loads are compared showing a good agreement in their deformations at the crest. Appropriate parameters including equivalent number of cycles and peak ground acceleration (PGA) for unique equivalent harmonic load were obtained based on the response analyses.