The Quaternary Strata profile and its variations of grain size in Yulin area reveal that: the layers of sand, loess, and palaeosol in the profile were respectively formed by wind for-ce and the action of soil formation on the parent materials of aeolian sand and loess.Since the early Quaternary, the Ordos Plateau has alternately undergone 11 stages of the depositions of shifting sands under extreme cold-dry climatic conditions, 7 times of fixed-semifixed dunes and 8 times of dust (loesses) under cold-dry climatic conditions; and that of the action of soil formation under 15 times of warm-wet climate and 3 times of temperate-wet climate (drab soils and black loams formed respectively).