Sour yak milk， Tibetan mushroom Yogurt and Qula are traditional dairy products made by Tibetans in Gansu Tibetan areas， the bacterial communities contained in them play an important role in their quality. This paper took traditional yak fermented dairy products produced by different Tibetan families in Tibetan areas of Gansu as the research objects. The Illumina MiSeq high-throughput sequencing platform was used to study the diversity and community structure of bacteria in three major categories of nine traditional dairy products， correlation analysis of bacterial community distribution combined with different samples. Finally， 511 070 high-quality 16S rRNA gene sequences were obtained， a total of 5 bacterial gates were identified， 11 different bacterial genus. Among them： Firmicutes and Proteobacteria are dominant bacteria gates， Lactobacillus and Streptococcus are high abundance genus in various samples， followed by Macrococcus and Lactococcus. Different types of traditional yak fermented dairy products had different bacterial communities. The function of PICRUSt indicate that basically functional prediction dominates. The results of this thesis could provide the necessary theoretical basis for the study and protection of excellent bacteria in traditional yak fermented milk in Tibetan areas of Gansu.