Abstract: Based on the observation and analysis under the polarizing microscope, the difference of fabrics between the loess and paleosoil of the Zektai profile in Gongnaisi county of Yili prefecture in Xinjiang is distinct. The type of the loess fabric is fine silt, sand-mosaic, porous-porphyric cementation. The type of paleosoil fabric then belongs to fine silt clay, scattered-mosaic, porphyric-basal cementation. The kinds of their minerals have no evident different, then, the relative contents of minerals vary. The primary minerals in the paleosoil relatively decrease, and the contents of secondary and altered minerals increase. The dissemination of iron is commonly seen. On the other hand, solution-precipitation makes mineral become more fine or form clay mineral and particle aggregate of secondary calcium carbonate and microcrystal which fill in secondary large porous. These characteristics of fabric and mineral composition, which are hardly seen in the loess, are the result formed by relative warm and wet environment. From that, the conclusion can be deduced that：the climate has the state of cold-warm and dry-wet alternation in the process of forming the Zektai loess.

Key words: Loess and Paleosoil, Fabric, Mineral composition, Zektai profile