Geosynthetic reinforced soil (GRS) walls and slopes have become important applications of retaining structures in earthquake prone areas such as Taiwan and Japan in Asia. In this paper, the authors present a numerical model that is capable of simulating seismic response of GRS structures. Results of GRS slope shaking table tests that were conducted in University of Washington were then utilized to verify the developed model. Moreover, a selected modular block faced GRS wall, which failed during the 921-Chi-Chi earthquake, was carefully analyzed with the developed model using real earthquake records. Seismic performance such as deformation history, reinforcement strain distribution, as well as failure mechanism of the studied case was examined in this paper. Additional efforts were also made to examine the influence of seismic design factors such as peak ground acceleration, duration, and frequency via a preliminary parametric study. Conclusion of presented research was hoped to be helpful to improve the understanding of seismic behavior and the design of GRS structures.