The displacements of reinforced soil retaining walls under seismic loads have a significant influence on their seismic performances. In order to calculate the displacements under earthquakes

Newmark’s sliding block method is usually used in design.As the traditional Newmark’s sliding block method neglects changes of soil strength

so the peak or residual strength is used in calculation

which lead to the calculated values being smaller or bigger than the actual values. Under the assumption of a two-wedge failure mechanism

sliding safety coefficient of reinforced earth retaining walls is obtained using the mechanical equilibrium equations of wedges. At the same time

the strain softening characteristic of backfills is considered by introducing thresholds of displacements. The following conclusions have been obtained by comparing the calculated values with the model tests. Compared with the single wedge method

the two-wedge method can better describe the actual failure mode of model walls and the calculated yield acceleration coefficient is closer to the test values. Compared with the calculated displacements by using the peak or residual strength

the calculated values from the proposed method where strain softening is considered is closer to the model test values.