Abstract: Ulcerative colitis (UC) is defined as a chronic inflammatory disease with recurrent episodes, and current therapeutic strategies for this gastrointestinal disorder often fail to achieve satisfactory clinical outcomes. This clinical challenge underscores an urgent requirement to develop alternative treatment strategies. Patchouli alcohol (PA), a natural compound exhibiting anti-inflammatory and antioxidant properties, has shown potential; however, its precise mechanisms of action in UC remain to be fully elucidated. Our study shows that PA can effectively alleviate the symptoms of dextran sulfate sodium (DSS)-induced UC in mice. This therapeutic effect is achieved by reducing intestinal barrier impairment and inhibiting inflammatory reactions. In an LPS-induced inflammatory model using RAW264.7 cells, PA significantly downregulated the mRNA expression of il-1β and il-6. Mechanistically, protein disulfide isomerase (PDI) was identified as a direct target of PA. By inhibiting IRE1 activation via PDI, PA mitigates endoplasmic reticulum stress, thereby reducing intestinal epithelial injury and ultimately alleviating the severity of UC. In this research, it is determined that the ability of PA to protect the intestinal epithelial barrier is brought about by its specific targeting of PDI, which alleviates consequent endoplasmic reticulum stress and prevents cellular damage.