China is a multinational country composed of 56 ethnic groups of which the Han Chinese accounts for 91.60％.Qinghai Province is located in the northeastern part of the Qinghai-Tibet Plateau,has an area of 72.12 km2,and is the fourth largest province in China.In the present study,we investigated the genetic polymorphisms of 20 short tandem repeat (STR) loci in a Qinghai Han population,as well as its genetic relationships with other populations.A total of 273 alleles were identified in 2 000 individuals at 20 loci,and the allelic frequency ranged from 0.0002 to 0.5327.The 20 STR loci showed a relatively high polymorphic rate in the studied group.Observed and expected heterozygosities ranged 0.613 0-0.907 5 and 0.614 8-0.920 0,respectively.The combined power of discrimination,and the probability of exclusion in duo and trio cases were 0.999 999 999 999 999 999 999 999 34,0.9999960 and 0.9999999965,respectively.Analyses of interpopulation differentiation revealed that the most significant differences were found between the Qinghai Han and Malaysian,while no significant differences were found between the Qinghai Han and Han people from Shaanxi and Jiangsu.The results of principal component analysis,multidimensional scaling analysis and phylogenetic reconstructions also suggested the close relationships between the Qinghai Han and other two Han populations.The present results,therefore,indicated that these 20 STR loci could be used for paternity testing and individual identification in forensic applications,and may also provide information for the studies of genetic relationships between Qinghai Han and other groups.