A series of laboratory tests was carried out fur analyzing of seepage characteristics of two-layers embankment model which consists of gravel and earth fill layers. Gravel layers were built under the earth fill for a half and one-third width of earth fill of the model. Permeability of earth fill was ranged between $5.00 imes10^{-5}~3.00 imes10^{-4};m/s$.. The tests were performed with hydraulic gradients(i), $0.10~0.55$. From the test results, hydraulic head of earth fill with gravel layer was 1.6 times higher than that of earth fill without gravel layer. Seepage rate was increased up to $4~22$ times and safety factor for piping was decreased to $13~43;\%$ comparing the earth fill with gravel layer to that without gravel layer. The gravel layer under the earth fill could, in general, give some serious seepage problems to seadike embankment.