Inflammatory bowel disease (IBD) is a chronic intestinal disease, which was commonly found in westerners whereas is increasingly prevalent in Asia because of the changing eating habits. In previous research, we found that a water-soluble polysaccharide isolated from Auricularia auricular-judae (Bull.)-a kind of edible mushroom (Aap)-is composed of β-1,3 glycosidic bonds, which is regarded as therapeutic or protective substance in enteritis. We therefore aimed to find the preventing effect of Aap on IBD. Here, we reported that pre-administration of Aap not only ameliorated weight loss, colon damage, and mucosal inflammation in colitis mice, but also prevented the damage of intestinal barrier by reducing the D-lactic acid and diamine oxidase level in plasma. Through high-throughput sequencing, we found that Aap changed gut microbiota composition. Furthermore, the preventing effect was transmissible via horizontal feces transfer from Aap-treated mice to normal mice. Our results indicated that oral administration of Aap is a promising protective substance of IBD. PRACTICAL APPLICATION: Our study proved that Auricularia auricula polysaccharide had substantial preventing effect on DSS-induced colitis in mice. This research might lay the theoretical foundation and technical support for the development of related functional foods. People could also enhance their gut immunity by eating Auricularia auricular in their daily life. Auricularia auricular as a highly nutritious agricultural product showed the broad significance in nutrition and food function.© 2020 Institute of Food Technologists®.