Based on the Cyclic Mobility (CM) model, a modified elasto-plastic model with rotation hardening which could systematically describe the monotonic and cyclic mechanical behaviors of soils combining the subloading, normal and superloading yield surfaces, is employed in the static and seismic stability analysis of embankment dam. By using the degree of saturation as independent state variable, this model could uniformly describe the behavior of unsaturated soil and saturated soil. By the transform stress method, this model could uniquely describe the overall mechanical properties of soils under general stress states, without changing the values of parameters. This model is suitable for three-dimensional static-dynamic analysis for complex embankment dam and foundation. Simulation reappears the disaster process of typical embankment dam in Wenchuan earthquake, and the results agree well with the phenomena of field survey, which indicates that the proposed method is sufficient for simulating seismic disaster process of embankment dam. Furthermore, the influence of PGA of input ground motion on the elasto-plastic seismic response analysis of embankment dam is studied.