Abstract: The Quaternary Pleistocene wind\|blown loess layer is widely distributed in north Tianshan mountain area of China, which belongs to the low liquid limit silt which has less cosmid and higher content of water soluble salt. According to the identification test of dispersive clay in current code, the silt is dispersive, Therefore, for the identification of dispersive soil, it is not only to macro judge from its topographic feature and lithology in the field, but also to combine with the tests in the lab such as particle analysisi test and ion content test.