Laying a flexible cushion or backfilling lightweight soil behind the retaining wall has important engineering significance for its optimized design and cost reduction. By carrying out model tests of retaining walls with different level of loads, the magnitude and distribution characteristics of the lateral earth pressure when laying EPS flexible cushion, backfilling lightweight soil and applying it at the same time are analyzed, and the load-reducing effect is discussed. The result shows: when the retaining wall is paved with flexible cushion, backfilled with lightweight soil, or both are applied, the lateral earth pressure shows a "bulging" nonlinear feature that increases first and then decreases with the burial depth, and the maximum value of earth pressure often appears at half of the wall height; under the same load, the load-reducing effect of backfilling lightweight soil is relatively weak, the load-reducing rate is 10%-25%, the maximum load-reducing rate of laying a flexible cushion is increased by 1.5 times compared with lightweight soil, when both two are applied, the load-reducing effect is the strongest, and the maximum load-reducing rate is increased by nearly 3 times; the load-reducing effect of the flexible cushion decreases with the variation of thickness, the foam content is more sensitive to the load-reducing rate of the backfill lightweight soil. In the engineering project, a medium-thickness cushion is optimal choose, if the applying load of the backfill is large, the content of the backfill lightweight soil can be appropriately increased.