Situated on the southeastern margin of the Badain Jaran Desert in China,The CGS3a segment of the Chagelebulu section contains 5. 5 sedimentary cycles which consist of aeolian dune sands or loess alternating with overlying lacustrine facies during the OIS3a. The analyses of grain - size Mz( phi) and sigma,Rb and Sr contents and Rb /Sr ratios for 140 samples showed that the values of Rb and Sr contents and Rb /Sr ratios in lacustrine facies are generally higher than those in dune sands or loess,with correlation coefficients between Rb,Sr and Mz more than 0. 8; and the graph of Rb and Sr contents and Rb /Sr ratios shows 5. 5 oscillations similar to the sedimentary cycles. Thus,the CGS3a segment probably experienced 5. 5cold - dry and warm - humid climate cycles in the alternations between the East Asian winter and summer monsoons during the OIS3a. Besides,the warm climate changes in the CGS3a correspond well to the Dansgaard - Oeschger events in the GRIP,and the cold period also corresponds well to the Heinrich Event. The climate changes on millennium - scale in the CGS3a actually record the evolution of the East Asian monsoons,and it is the regional response to the global climate changes during that period.