Objective To analyze the expression of IL-18 and changes of intestinal flora in tree shrews under the action of D-galactose. Methods Ten male tree shrews were randomly divided into normal and D-galactose groups (n = 5). Intraperitoneally injected D-galactose (0. 6 g / kg) for 8 weeks was applied to the D-galactose group. Tree shrews in the normal group were injected with normal saline in the same manner. The ileum of the small intestines and the cecum and colon of the large intestines were separated, and their contents were collected. Expression of IL-18 was detected by immunohistochemistry. The bacterial 16S rDNA sequence in intestinal contents was analyzed by high-throughput sequencing. Results Immunohistochemistry showed that the expression of IL-18 in the ileum, cecum, and colon was significantly increased in the D-galactose group P<0. 05). The abundances of enterobacteriaceae and aeromonas in the cecum and colon were increased significantly in the D-galactose group. The abundance of bifidobacteriaceae was decreased in the colon of the D-galactose group. Conclusions D-Galactose increases the expression of intestinal inflammatory factor IL-18 and causes intestinal flora disorder, suggesting that the imbalance of intestinal flora in tree shrews caused the increased expression of IL-18 and promoted the intestinal inflammatory response