Abstract: Based on the test results of sand-loess around the Daliang Reservoir of the Wanjiazhai water diversion project, the Characteristics including composition, physico-chemical properties and mechanical properties are summarized. By comparison of the sand-loess microstructures under different states, the applicability of sand-loess as filling material to a reservoir dam, as well as the engineering problems associated with the sand-loess slopes and tunnels, is discussed.