The desert and Gobi deposition are prevailing in the west edge of the middle Helan Mountain,which is subject to the frangibility of eco-environment.It is important to explore the relationship between the climate change and deposition response of Gobi desert since the Last Glacial,apluvial profile of late Late Pleistocene on the east edge of Tengger desert is employed to rebuild the palaeoenvironmental change based on the phytolith analysis.On the basis of regional geological survey,geomorphology pattern and Quaternary sediment distribution in the west of middle Helan Mountain and east edge of Tengger desert were investigated in detail.Based on the AMS~(14) C dating and phytolith records,paleovegetation and paleoclimate changes are reconstructed in detail.Relatively abundant phytolths are found in the pluvial sediments of Qp_3-Qh profile at the Yaoba,including the following morphotypes:parallelepipedal bulliform cells(including square-and rectangle-shaped)and cuneiform bulliform cells(fan-shaped),bilobate,rondel,trapeziform sinuate,elongate and unciform hair cell(point-shaped),elongate smooth, elongate echinate,elongate protuberant,and prism,etc.In addition,there are abundant charcoals and burnt phytoliths in the sediments,indicating the history of ancient human activities.Phytolith assemblages with the warmth index analysis have rebuilt the history of paleovegetation and paleocliamte changes in the past 26 ka,showing 7 evident stages as follows:cool-dry,warm dry,warm-humid,cold-humid,cold-dry,warm-dry,and warm-humid.Our results demonstrate that the sedimentary environment of pluvial fan margin has a good response to the drought and wetness change of climate.The variation of the drought and wetness has a close relation with the regional desertification and ancient human activities.