The Qiang people are widely recognized as a basal layer of the Chinese gene pool, yet their genetic origins and evolutionary history remain unclear. We analyzed 20 deep-sequenced Qiang genomes together with genomic data from Tibetan highlanders and neighboring lowlanders. The Qiang genetic structure has been profoundly shaped by historical admixture with Han and Tibetans, giving rise to distinct subpopulations. Using ~450 ancient Asian genomes, we traced the most recent common ancestor of the Qiang to ancient Yellow River farmers ~5300 years ago, indicating shared ancestry with other Chinese populations. We identified several highly differentiated variants related to ethanol metabolism and pigmentation between Qiang subpopulations, which likely arose from joint effects of admixture and selection. Notably, a highly prevalent missense variant in a blood pressure regulation gene was detected, suggesting a potential role in altitude adaptation. Collectively, our findings illuminate the genetic history of the Qiang and highlight how admixture and selection shaped the diversity of Tibetan-Plateau fringe populations.