A sandwich dune's profile consists of layers with different soil textures, the upper and lower of which are sandy soil layers, and there is a fine soil pan between the surface and the subsoil. The clay interlayer is composed of silty loam containing over 90% silt and clay. Deposits of this layer occur at depths of 120-500cm and it ranges in thickness from 40 to 100cm. In arid areas with precipitation of less than 200mm, artificial sand-fixing vegetation coverage is approximately 10% to 15%; however, the vegetation coverage of the study area with 117mm mean annual precipitation is approximately 65%, which does not meet the zonal water and heat conditions. Water retention is considered to play an important part in affecting the water conditions and soil water carrying capacity of dunes. With regards to water retention, Betti et al. have analyzed the effects of soil texture on water retention, revealing that when the sand content is increased, water retention becomes weaker, and the soil layer has a significant effect on the water-holding capacity, and their studies have focused on analysis of the water-holding capacity of homogeneous soil. In order to study the characteristics and mechanisms of the response of the clay interlayer to water retention, we measured the soil water characteristic curve based on the centrifuge test, particle size measured by Mastersizer-2000, and pore distribution based on the measured soil water characteristic curve and the calculated equivalent porosity at different depths of a sandwich dune. Our results show the following patterns. (1) The soil moisture content of the clay interlayer was the highest, soil water content increased slightly with depth in the surface soil, and the soil moisture of the subsoil was higher than in the surface, which was affected by the capillary action of groundwater. (2) Field capacity, wilting coefficient, saturated water content, total porosity, and aeration porosity were significantly correlated with soil physical properties, such as bulk density, sand content, clay content, and particle size. Sandy soil layers were at 0-4.0m and 4.6-8.0m. The soil water characteristic curves of these profiles were steep and the soil was loose (aeration porosity, 14%-27%) with poor soil water retention. The layer at 4.0-4.6m was an interbedded layer of silty loam, the soil water characteristic curves of which was smooth and the soil water content was high when the soil water suction was high.This type of soil had less aeration porosity, leading to higher soil water-holding capacity than the upper and lower sandy layers. Furthermore, correlation analysis showed that capillary porosity was not significantly correlated with soil physical properties, but was weakly related to soil water content, and increased significantly only at both the interface between the sandy layer and silty loam layer, and the water table. To a certain extent, the distribution of soil porosity affected the soil moisture content and water conveyance between the clay interlayer and the sand layer. In conclusion, soil textures lead to considerable differences in soil water retention of dunes at the edge of an oasis. The clay interlayer can hold more water compared with all profiles, which improves the water conditions of the dune. (3) The soil pan is the region where water collects, and provides water resources for plants. It plays an important role in the improvement of sand-fixing vegetation of dunes at the edge of an oasis. Further, the ability of the clay interlayer to regulate the water conditions of dunes depends on soil water retention and soil capillarity. In conclusion, our findings should provide strong support for future understanding of the mechanism of spatial patterns of artificial sand-fixing vegetation.