Being regarded as an elementary contact unit in the foundation and embankment of levees, trenches and other engineering constructions, the soil-structure interface is highly susceptible to erosion by unpredictable seeping water. This phenomenon can be increasingly complex when cohesionless aeolian sand, widely distributed in arid and semiarid regions with a narrow gradation and a poor compression behavior, is involved at the interface erosion. In an effort to enhance the understanding of such erosion seldomly in the spotlight, an interfacial seepage apparatus is developed and employed in this paper to investigate the influence of three impact factors, namely layer order, interface roughness characteristics and near-interface concentration path. It is found that a specified layer order (aeolian sand on top) evinces an apparent irrelevance of interface characteristics and the high critical hydraulic gradient (HCHG) is the lowest. Test analysis based on post-erosion surface status reveals an ambiguous effect of interface roughness characteristics, depending on the form of roughness patterns. Near-interface concentration path holds a potential to alter the erosion progression from interface erosion to vertical internal erosion within sands, suggesting in the meantime that the erosion scale is significantly magnified despite limited variance of HCHG between comparative cases.