Abstract:This study investigated the quantity and biodiversity of Bifidobacterium in the intestines of Mongolian people in Hohhot and Tongliao， Inner Mongolia， and explored the influence of region on the quantity and biodiversity of Bifidobacterium in people's intestines. With 50 Mongolian adult volunteers from Hohhot and Tongliao， Inner Mongolia as the research objects， specific primers of Bifidobacterium were used. The number and biodiversity of Bifidobacterium in the intestines of volunteers were analyzed by PacBio Sequel II sequencing technology and droplet digital polymerase chain reaction （ddPCR） technology. The average biomass of Bifidobacterium in the intestine of volunteers from Hohhot[（1.64×108±2.16）CFU/g]was lower than that of volunteers from Tongliao [（2.04×108±3.72 ）CFU/g]. A total of 11 species of Bifidobacterium were annotated in the intestine of volunteers from Inner Mongolia. There was no significant difference in the diversity and structure of Bifidobacterium in the intestine of volunteers from the two regions. However， B. angulatum， and B. longum were enriched in the intestines of volunteers from Hohhot （P＜0.05）， while B. dentium， B. catenulatum， B. biavatii， and B. thermacidophilum were significantly increasing in those of volunteers from Tongliao. According to Spearman analysis， the interaction network between Bifidobacterium in the intestines of volunteers from Hohhot was denser （P＜0.05， |R|＞0.3）. Compared with diversity and structure， geographical factors significantly affect the relative abundance and interaction network relationship of intestinal Bifidobacterium.