The Tibetan antelope (chiru, Pantholops hodgsoni), a heavily poached species and symbol of the Qinghai-Tibetan Plateau (QTP), is noted worldwide for its special calving migration. This species originated in the early Quaternary and it is interesting to know how the following climatic oscillations affected its demographic dynamics in the climate-sensitive QTP. In this study, we analyzed the mitochondrial D-loop region from 312 individuals sampled in all of the six major populations. We found high rates of gene flow and little genetic differentiation between populations, suggesting that the calving migration may have homogenized the genetic pool of this species. Both mismatch distribution analyses and coalescent simulations suggested that this species experienced a demographic expansion approximately 600-200 Kyr following the retreat of the large glaciers developed in the QTP at 800-600 Kyr, rather than at the end of the last glacial age, as previously suggested, based on a limited sample size. In addition, we found evidence of a chiru population decrease probably related to the human settings at the QTP during the middle Holocene.