Objective: To explore the preventive effect of high pressure assisted water extraction and enzymatic extraction of apple peel dietary fiber on ulcerative colitis in mice. Methods: A mouse model of colitis was constructed by dextran sulfate sodium. Enzyme-linked immunosorbent assay， histopathological analysis， 16S rRNA high-throughput sequencing， gas chromatography and other methods were used to analyze the changes of intestinal flora and short-chain fatty acids in mice after apple peel dietary fiber intervention and their relationship with intestinal inflammation and serum oxidative stress levels. Results: Apple peel dietary fiber could significantly reduce the level of intestinal inflammation in mice， improve the structure of colon tissue， up-regulate superoxide dismutase， down-regulate the expression of malondialdehyde and myeloperoxidase， and increase the content of short-chain fatty acids in the intestine. It was proved that the high-pressure-assisted water-extracted apple peel dietary fiber was better than the enzyme-extracted apple peel dietary fiber in alleviating colitis in mice. The results of intestinal flora analysis showed that the intestinal microbial diversity was dose-dependent with the intervention of apple peel dietary fiber. After the intervention of apple peel dietary fiber， the intestinal Bacteroidota and Lachnospira of mice were enriched， and the abundance of Proteobacteria and Parasutterella was reduced. Conclusion: Apple peel dietary fiber could reduce intestinal inflammation and regulate intestinal flora. This study provided a safer and more beneficial choice for the prevention of enteritis， and provides a theoretical basis for the development of apple peel dietary fiber functional foods.