Previous studies have demonstrated that the Chinese medicine paeoniflorin, derived from the Ranunculaceae plant peony, peony, purple peony root, was able to have anti-inflammatory, anti-ulcer, anti-hypersusceptibility and anti-oxidation activity. In order to elucidate the pesticide effect and the mechanisms by which paeoniflorin exerts its effect of anti-inflammation and immunoregulation on oxazolone-induced colitic mice, disease activity index (DAI) and histological grading of colitis (HGC) were evaluated in animal model. Moreover, the expressions of HBD-2, IL-6 and IL-10 of mice with experimental colitis were observed with immunohistochemistry and RT-PCR in this study. Results showed that DAI and HGC of oxazolone control group was significantly higher than that of normal control group, and that paeoniflorin groups and 5-ASA group, compared with oxazolone control group, could alleviate the symptoms and histological damages of colitic mice (P < 0.05, P < 0.01). The expression of HBD-2 and IL-6 cytokine on the colon of colitic mice was higher than that of normal control, paeoniflorin and 5-ASA groups (P < 0.05, P < 0.01), but the expression of IL-10 is lower than that of normal control, paeoniflorin and 5-ASA groups (P < 0.05, P < 0.01). The positive correlations were demonstrated between the expression of (HBD-2 and IL-6) and DAI (Pearson r = 0.728, Pearson r = 0.758, P < 0.01, respectively), (HBD-2 and IL-6) and HGC (Pearson r = 0.819, Pearson r = 0.825, P < 0.01, respectively), whereas, the negative correlations were demonstrated between the expression of IL-10 and DAI (Pearson r = -0.789, P < 0.01), IL-10 and HGC (Pearson r = -0.725, P < 0.01). It can be concluded that to some extent paeoniflorin effectively alleviate the symptoms of oxazolone-induced colitis through regulating the expression of HBD-2, IL-6 and IL-10.