Abstract: As the most tremendous transverse dune­mountain system in the world，the Badain Jaran Desert is located in the west part of Inner Mongolia Autonomous Region of China. Its formation mechanism has been the desert field problem of concern，in which the geomorphic and sedimentary structures are both basic and key issues. With GPR technique，profile detections had been made on two typical windward slopes of transverse dune­mountain in October of 2007.One is at Hudugo Jaran，and the other Nurtu，both of them were in the southeastern part of the desert，where dune­mountain system is the highest in the whole desert. The Hudugo Jaran slope is as high as 372m above its lake(lake Hudugo Jaran)level，detected in turn with 12.5MHZ(1m between two successive detecting points),25MHZ(1m space between),50MHZ(0.5m space between),100MHZ(0.5m space between)，respectively，and the Nurtu slope 421m above its lake(lake Nurtu)level with 50MHZ(1m space between). Because of the dissimilarity of humidity of sand layer，the probing depth was less than 100m or so，but the effective thickness of structural sand layer detected generally less than 30m. There existed 4 kinds of sedimentary facies according to the relationship of geomorphology and deposition structure in the depth range probed from the bottoms to the top of the whole sections. The first was a facies of fixed dune stabilized by Grass and shrub，which was distributed near the lake shore. The second was a simple transverse dune facies formed dominantly by the foreset laminae of ancient crescent­shaped dune，which was generally located in the lower range of slope，and was exposured as wind erosion plane. The third is a complex facies of ancient multi­tansverse dune that is usually situated in the upper segment of slope，consisting of different kind of laminae of transverse dune. And the last was a star­shaped dune facies，commonly perched on the top of the dune­mountain，with foreset laminae parallel to corresponding slope planes，and is exposed on both western and eastern slopes. According to the relationship of the layer sequence among all the segments and their inner parts detected，there very likely existed a sandy layer sequence with huge thickness under the slope of winward(i.e. west)side of the transverse dune­mountain，which was covered by modern secondary dunes. There existed wet sandy bodies in the inner parts of the sandy mountain bodies. Humid sandy layer generally happened under the middle and upper slope surfaces by 20～30m. Moisture were exposured on the surface of lower part of the slope. The water content of sand in the internal sand mountain may come mainly from precipitation，and be an important factor to form the sand mountain bodies and the lakes. The lakes of inter dunemountains may have closely related to some certain developing stages of the dunemountains or the sandy desert.