Abstract: The distribution of 4 red cell blood group systems was investigated on 104 "Ben Ren" students whose parents and grandparents are "Ben Ren" too, in Mulaoyuan Xiang, Shidian County, Yunnan Province. The results showed that in ABO system, the gene frequency p(0.3069) was larger than the gene frequency q(0.1739); in MNSs system, gene frequency m(0.6538) was larger than the gene frequency n (0.3462); in P system, the gene frequency p1 was low(0.1796). All these results tallied with the characteristics of southern ethnic groups in China. In the Rh system, like most populations in China, the CDe frequency(0.7980) of "Ben Ren" was larger than that of cDE(0.1322). Other gene frequencies were as follows: r=0.5192; MS=0.0288, Ms = 0. 6250, Ns=0.3462, S=0.0288, s=0.9712; C=0.7981, c=0.2019, D=0.9302, d=0.0698, E=0.1321, e=0.8679, and the haplotype frequencies of NS, cDe, CDE, cde, Cde and CdE were all zero. The genetic distances and phylogenetic tree obtained on the basis of gene frequencies of 4 loci of "Ben Ren" and 17 populations show that the "Ben Ren" is genetically close to Vazu, Achang, De'ang and other southern ethnic groups, but has long genetic distances with Northern ethnic groups and Han in Heilongjiang Province. However, there are eloquent evidences showing that the "Ben Ren" are offspring of Qidan, a Northern nomadic ethnic group some 1000 years ago. It can be concluded that the "Ben Ren" has mixed to a great extent with the local ethnic minorities of Yunnan Province.

Key words: Red cell blood groups; Gene frequency; "Ben Ren"; Qidan