Lactobacillus G15 and Q14, two species of Lactobacillus used in the preparation of Chinese traditional fermented dairy foods, have the potential to prevent diabetes. Herein, we clarified their mechanisms by which gut microbiota relate to the control of diabetes. Results showed that G15 and Q14 improved the disorders in blood glucose and insulin. Moreover, G15 and Q14 promoted the enrichment of SCFA-producing bacteria, and upregulated the production of acetate and butyrate. Their antidiabetic effects were closely associated with SCFAs-downstream receptors and hormone secretion. Additionally, G15 and Q14 significantly shortened the number of G-negative bacteria, which subsequently decreased the levels of LPS and inflammatory factors. G15 and Q14 improved the disorganization of the intestinal mucous and the integrity of intestinal barrier. Our results indicate that Lactobacillus G15 and Q14 alleviate type 2 diabetes in a gut microbiota-dependent way via downregulating G− bacteria-related LPS secretion, as well as upregulating SCFAs-producing bacteria-related G protein-coupled receptor 43 pathway.