Abstract:  Lactic acid bacteria(LAB) and yeasts involved in production of traditional fermented yak milk products which are made by herdman families in Tibet area,were enumerated and isolated,and the strains of LAB were identified using conventional identification methods and 16S rRNA gene sequence determination method. The results showed that in 3 fermented yak milk,samples,the LAB and yeast counts range from 1.04×104 to 2.10×106 CFU/ml and from 8.20×103 to 6.70×105 CFU/ml,respectively,and in 2 cheese samples,the LAB and yeast counts range from 0.2×10 to 1.0×10 CFU/g; 15 Strains of Lactobacillus,4 stains of lactic acid cocci and 3 stains of yeasts were isolated from fermented yak milk; The LAB species are identified as 10 strains of Lactobacillus paracasei(55.6 % of the total LAB strains ),1 strain of Lactobacillu fermentum,2 strains of Lactobacillus reuteri,1strain of Lactobacillus brevis,1 strain of Lactobacillus delbrueckii subsp.bulgaricus,2 strains of Pediococcus acidilactici and 2 strains of Pediococcu and Lactococcus which can not be identified according to the present method.

Key words: Tibet, fermented yak milk, lactic acid bacteria, isolation and identification