Objective：We aimed to investigate the effects of a secondary bile acid deoxycholic acid(DCA)on the gastric microbial community in INS-GAS(Insulin-Gastrin)mice model of intestinal type gastric cancer. Methods：Ten 8-week-old male INS-GAS mice were randomly divided into two groups，one group was given 0.2% DCA drinking water，and the other group was given normal saline (NS)solvent. Another 5 male FVB/N wild -type mice in the same litter were given 0.2% DCA as a genotype control group. After 3 months of drinking water intervention，the gastric contents of each group were collected for 16S rDNA amplicon sequencing，and the relative abundance of gastric microbiota，α diversity，β diversity and significantly different species were analyzed. The gastric body and antrum mucosal tissues were isolated respectively，and the mRNA expressions of intestinal markers cdx2，klf5，vil1 and muc2 were detected by qRT-PCR. Results：Compared with the NS group，DCA treatment changed the dominant bacteria in the stomachs of INS- GAS mice，and the bacteria with the highest relative abundance on the level of genus changed from the Lactobacillus(61.93%)to the undefined Cyanobacteria genus（58.70%）. There were no remarkably differences in the abundance and diversity of gastric microflora between the two groups（ACE index P=0.213，Chaol index P=0.280；Shannon index P=0.391，Simpson index P=0.205）. Principal component analysis found that the two groups had a considerable difference in the structure of the gastric microbiota，and the difference between the two groups was greater than the difference within the groups（R=0.368，P=0.032）. DCA treatment significantly increased the abundance of Cyanobacteria in the stomach of INS -GAS mice at the levels of phylum，class，order，family and genus，and also upregulated the abundance of the Anaerostipes genus and the Cyanobacteria genus Lolium perenne and Phaseolus vulgaris. In addition， significantly higher enrichment of Lactobacillus including Lactobacillus reuteri，belonging to the phylum Firmicutes was found in gastric contents of INS -GAS mice drinking DCA compared with the control group. The expression of muc2 mRNA in the gastric body and antrum mucosa of INS-GAS mice drinking DCA was considerably higher than that of INS-GAS mice drinking NS（both P < 0.05）. The abundance of gastric microbiota in the stomach of INS-GAS mice with the same DCA intervention was significantly higher than that of FVB/N mice（ACE index P=0.022；Chao1 index P=0.028）. However，INS-GAS（DCA）and FVB/N（DCA）mice had greater differences within groups than between groups（R=-0.056，P=0.647）. Conclusion：DCA intake changed the structure of the gastric microbiota of INS-GAS mice. The relative abundances of Cyanobacteria and Anaerossipes were significantly increased，while the relative abundance of Lactobacillus decreased，and promoted the expression of Muc2 mRNA.