Reaumuriasoongarica (Tamaricaceae) is aTertiary relic species widely distributed in northwestern China as one of constructive and dominant species in desert ecosystems.The spatial and temporal patterns of genetic diversity withinR.soongarica populations and the relationship between their demographic historiesand aridification of northwestern Chinaare not fully understood yet.To test the hypothesis that its evolutionary history was influenced by Quaternary climatic oscillations and aridification of northwestern China, 14 unlinked random nuclear loci with length ranged from 381 to 1734bp, were sequenced in 328 individuals from 41 R.soongaricapopulations, to estimate the genetic diversity within/among populations which sampled from all the desert regions of northwestern China.First of all, standard neutrality tests and MDFM test wereconducted to test the likelihood of adaptiveevolution of each locus.Based on the loci nearly neutral, Isolation-with-Migration model (IM model) was then applied to determine the divergent time andpotential gene flowbetween different populations.To furtherprofile the historical change of effective population sizes from different geological regions andto simulate the most reasonable evolutionary scenarios which shapedthe current patterns of genetic variation, Approximate Bayesian Computation (ABC), Bayesian skyline plot and (o)a(o)ianalysis were used for the populations from each local region.Together with the help of ecological niche modeling (ENM) to summarize the range shift in the history, we are able tounderstandthe most parsimonious evolutionary scenario of this desert shrub species.Thisstudy willalso support molecular phylogeographic evidences to understand theasynchronous aridificationprocesses ofthe local regions of northwestern China.