The MIS 3 sequence of Tumen Section(TMS 3)in the southern margin of Tengger Desert was composed by paleo-aeolian sand,loess-like sandy loams,sandy loess,paleosoil,lacustrine and alluvial loess. The results of grain size analysis showed the sand contents were dominants,silty sand contents were in second place,and clay contents were minimal in TMS 3,and their contents in average are 65.45%,26.72%and 8.83%,respectively;based on the sequence decreasingly in content,the sand contents can also be divided three portions,and they are fine sand,very fine sand and medium sand-coarse sand.The contents of medium sand-coarse sand and fine sand in paleo-aeolian sands were higher than other 5 sediments in TMS 3.These grain size cycles indicated the climate during MIS3in this area at least went through 13 warm-wet events and 12 cold-dry events and could divided into five substages:TMS3e(54 200-59 750 BP),TMS3d(54 200- 40 800 BP),TMS 3c(40 800-32 800 BP),TMS 3b(32 800-25 400 BP)and TMS 3a(25 400-22 940 BP).These fluctuations show a strong coherence with D/O events recorded in Greenland ice core and southern China stalagmites,as well,H events recorded in North Atlantic sediments.