Abstract: The stability of retaining walls constructed with soilbags is closely related to their interlayer friction. The difference of the interlayer friction of flexible soilbags from that of rigid bodies is investigated through the tests on the bags filled with aluminum rods. A series of laboratory tests are conducted to study the influences of the materials filled into bags, the inter-layered arrangements of soilbags and the water on the interlayer friction of soilbags. It is indicated from the experimental results that (1) The frictional force between two flexible soilbags increases with the interlayer displacement of soilbags, and reaches the maximum value at the beginning of the whole slippage between two soilbags and then tends to be stable; (2) The interlayer friction of soilbags is influenced by the bag friction, the grain sizes of filling materials and the interlayer arrangements of soilbags; (3) Owing to the lubricating effect of water on bags, the interlayer friction of the soilbags filled with fine materials decreases when they are placed underwater. However, the interlayer friction of soilbags filled with coarse meterials is slightly influenced by water.