Abstract: In order to explore the bacterial diversity in traditional fermented yak yoghurt,the traditional naturally fermented yak yoghurt samples collected from different areas of western Sichuan Plateau were analyzed by Illumina Miseq sequencing. The results showed that 8 sequencing samples had 375236 optimized sequences,with an anverage of 46905 sequences,a total of 88 different OTUs.The α-diversity index of the sample GC was the best,and the bacterial community diversity was the highest and the distribution was uniform. The only OTU number of two samples in Batang County was 31 compared with other counties. Eight samples were at the level of the phylum,the dominant bacteria was the Firmicutes,accounting for 98.33%~99.96%.At the genus level,the main bacterias were Lactobacillus,Streptococcus,Anoxybacillus,Macrorococcus and Weissella,Lactobacillus was the dominant genus of all samples,accounting for 69.31%~99.92%.According to the heatmap and PCoA of the samples,the community structure of 8 samples at the genus level was similar,with slight differences,and the community structure in yak yoghurt in different areas was different and similar. The results of this study provide a theoretical basis for the development and application of traditional fermented yak yoghurt in western Sichuan Plateau.