In order to explore the permeability characteristics of soilbags infilled with expansive soils, a large-scale permeability-test model box was developed. The permeability test was carried out according to the arrangement pattern of soilbags, water flow direction, water head and interlayer filling conditions. The experimental result showed that the horizontal permeability coefficient is greater than the vertical permeability coefficient. The infiltration water could be quickly discharged along the gap between the horizontal layers of soilbags, so that it was not easy to infiltrate into the compacted underlying layer of the expansive soil canal slopes. After filling the gaps between bags with expansive soils, the vertical permeability coefficient changed slightly, while the horizontal permeability coefficient decreased obviously. The permeability of soilbags infilled with expansive soils mainly depends on the size of the gaps. The effect of the soilbag arrangement on the permeability is essentially attributed to the changing of the gap number and shape. In practical, it is expected to provide more preferential flow paths along the horizontal direction if no compacted soils are infilled inside the gaps between soilbags during the actual construction conditions.