Abstract: In order to study the relieving effect of extracellular polysaccharides (EPS-A,EPS-B) which were extracted and purified from long shelf-life yogurt fermented by long shelf-life yogurt culture A and culture B, their molecular characteristics, structural morphology and monosaccharide composition were determined, and the mouse weight, influence of colon histopathology, the expression of inflammatory factors, the content of myeloperoxidase (MPO) and tight junction proteins (ZO-1, Occludin) in mice were also analyzed through constructing an animal model of colonic inflammation in mice by dextran sulfate sodium (DSS). The results showed that there were significantly differences on the molecular morphology and monosaccharide compositions between EPS-A and EPS-B. The EPS-A was slightly loose in structure, composed of three monosaccharides (galactosamine hydrochloride, galactose and glucose) with a molar ratio of 0.345:0.21:0.435. The structure of EPS-B was compact and it composed of four monosaccharides (galactosamine hydrochloride, glucosamine hydrochloride, galactose and glucose) with a molar ratio of 0.421:0.05:0.207:0.322. The weight of IBD mice was recovered in all the exopolysaccharide treatment groups, but there was no significant decrease in the disease activity index (DAI) score. The colon morphology of the high dose group of EPS-A was close to that of the blank control group, and there was no significant difference in colon length and colon coefficient between the two groups (P>0.05), the same below). Combined with the expression of inflammatory factor (TNF-α, IL-1β, IL-10) in different treatment groups, the high dose group of EPS-A had the best response to those inflammatory factors, and there was no significant difference between it and the drug treatment group (P>0.05). The expression of ZO-1 and occludin protein in the high-dose and low-dose groups of EPS-A was significantly improved and same as the drug treatment group (P<0.05). The expression of ZO-1 protein in the high-dose group of EPS-B was also significantly higher than that in the model group, but the effect was not as good as that in the EPS-A group (P<0.05). There was no significant improvement in reducing MPO activity in different extracellular polysaccharide treatment groups compared with the model group (P>0.05). In summary, it could be seen that EPS-A can significantly improve the enteritis of mice, and its effect was better than that of EPS-B.