Abstract: As a new kind of geosynthetics that can greatly reduce the earth pressure behind the retaining wall, the light weight soil has great application advantages in highway engineering and civil engineering. In order to study the characteristics of earth pressure at rest of the light weight soil with foamed particles, the influence laws of loading path, mixing ratio and filling depth on the earth pressure at rest and the coefficient of earth pressure at rest are investigated by the K₀-consolidation tests and model tests. The results show that the coefficient of earth pressure at rest of the light weight soil is related to the loading path and mixed ratio. In the model tests, with the increase of vertical stress, the relationship curve between lateral earth pressure and filling depth of the light weight soil gradually changes from a straight line to a broken one. As the load is removed, the relationship curve between lateral earth pressure and filling depth gradually recovers from a broken line to a straight one. In the process of loading and unloading, for the lateral earth pressure, an inflection point appears at the filling depth of h/2 with its increase, where there is a critical depth. In the model tests, the coefficient of earth pressure at rest of light weight soil is 0.34~0.48. Compared with the remoulded soil, the light weight soil has better self-supporting performance. The lateral earth pressure of the light weight soil behind the retaining wall is about 22%~30% of that of the remoulded soil, which can greatly reduce the earth pressure behind the retaining wall, indicating that the light weight soil has good engineering performance. Considering the unique structural characteristics of the light weight soil, based on the traditional formula for the coefficient of earth pressure at rest of the overconsolidated soil, the relative structural degree k is introduced to establish the formula for the structural static earth pressure coefficient of the light weight soil. The difference between the predicted and measured values of the proposed formula is verified by the results of K₀-consolidation and model tests, which indicates that the proposed fourmula has a higher accuracy than the Jaky formula.