The lacustrine sediments of Qiongduo Basin in the southern Qinghai-Tibet Plateau are studied by using AMS14C dating method,and the time series of 40ka BP~30ka BP of Qiongduojiang basin sediments is obtained.The TOC content,TN,the TOC/TN ratio anddelta~(13)Corg substitute indexes from 50samples of 5cm~250cm Qiongduojiang Basin lacustrine sediments are analyzed, and the paleoclimate change of 40ka BP~30ka BP in Qiongduojiang Basin is divided into several stages:the warm humid climate period(40.2ka BP~38.5ka BP),the warm arid climate period(38.5ka BP~35.4ka BP),the transition climate period(35.4ka BP~32.4ka BP),the volatility climate period(32.4ka BP~31.7ka BP)and shift to arid climate period(31.7ka BP~ 30.3ka BP).Spectrum analysis reveals that there are quasi-periodic climate variations of 1 552a, 1 187a,961a,602a,538aand 492afrom 40ka BP~30ka BP.Climate change at the millennium scale may be related to the effects of solar activity,atmospheric circulation,oceanic internal instability and monsoon activity.The identified 538acycle corresponds to the 530acycles of the solar activity,and therefore,the solar activity is also one of the causes of climate change in the Qongduojiang basin.