Abstract: The back-to-back mechanically stabilized earth (MSE) walls belong to a special type of geosynthetic-reinforced soil retaining walls. This type of walls are widely used in road construction projects that inherit the good seismic performance of GRS retaining walls, however, their seismic design methods at present are still not adequate. In this study, based on the calibrated PLAXIS finite element procedure, numerical simulations are carried out to investigate the seismic response of the back-to-back MSE walls. It is found that the back-to-back MSE walls show many similar dynamic characteristics with the GRS retaining walls when subjected to the earthquake loadings, including the maximum reinforcement loads, the residual lateral facing displacements and the settlements of backfill surface. There might exist a second failure surface from the analysis of the distribution of the reinforcement load in each layer. By fitting the numerical simulation results, it is also found that there exist good correlations among the maximum reinforcement loads, the input characteristics of earthquakes, and the frequency characteristics of structures.