Abstract: The Sandy desertified land in Sahelian region of Northern Mali amounts to 254 880km², occupying 55.3% of the area, and the sandy desertification is still in the intensely developing stage. Various eolian sands spreading widely on the surface is the material base for the occurrence and development of sandy desertification. The grain size composition of eolian sand in the region is dominated by fine sand, followed by very fine sand. Bacause of the impacts of sand origin, accumulation condition and development course, there are some differences in the features of grain size of various dune sand. The eolian sand consists of 26 minerals, among which 21 are heavy minerals, Occuprging 0.1-2.0 percent. The stable and very stable minerals are dominating in these heavy minerals, and the heavy minerals have high stability and maturity. The eolian sand in this region mainly originates from reactivation of ancient sand dunes, modern fluvial action, dry lake deflation and older river courses. According to preliminary study, there are at least 4 major periods of eolian sand development in the region, i.e. Pliocene-early Quaternary, last glacial period, Holocene and modern times; among them the Holocene has 3 aeolian stages, namely early Holocene (10.3-9.2 ka B.P.), mid Holocene (6.8-5.8 ka B.P.) and late Holocene (3.5-1.8 ka B.P.). In the orderly fluctuated courses of alternately dry humid changes in the global climate the eolian sand underwent development, expansionfixation and soil formation in the region.