Abstract: To determine the genetic polymorphism of three X-STR loci for Bai, Dai, Yi ethnic groups from Yunnan Prov-ince, DXS6804, DXS6799 and DXS7132 were genotyped by multiplex PCR and Genscan. Eighteen alleles and thirty-eight genotypes were detected in 89 Bai unrelated persons. The gene frequencies ranged from 0.0200 to 0.6400, and the geno-types frequencies ranged from 0.0256 to 0.3333. Seventeen alleles and twenty-four genotypes were detected in 100 Dai unrelated persons, with the gene frequencies ranging from 0.0135 to 0.7500 and the genotypes frequencies ranging from 0.0385 to 0.5769 respectively. There were 20 alleles and 35 genotypes detected in 88 Yi unrelated persons. The gene fre-quencies ranged from 0.0125 to 0.5875, and the genotypes frequencies ranged from 0.0250 to 0.3500. The genetic informa-tion demonstrated that the three loci are highly polymorphisms in Bai, Dai, Yi ethnic groups. Cluster analysis and phylo-genic tree showed the genetic affinity between Bai, Dai, Yi, and Tibet populations.