Objective To investigate the mechanism of melezitose(MELE)on ulcerative colitis(UC)by structing a mouse model of ulcerative colitis(UC)induced by dextran sodium sulfate(DSS).Methods Forty-eight SPF grade male c57BL/6 mice were randomly divided into normal group(0.9%NaCl),model group(0.9%NaCl),control group(100 mg·kg-1 mesalazine)and experimental-L,-M,-H groups(20,40,80 mg·kg-1 melezitose solution).The UC model was induced by giving 3%DSS solution instead of drinking water,and the disease activity index(DAI)was evaluated.Serum levels of interleukin-1 β(IL-113),IL-6,IL-10 and tumor necrosis factor α(TNF-α)were detected by enzyme linked immunosorbent assay.The expression levels of major histocompatibility complex Ⅱ(MHC Ⅱ)and cluster of differentiation 4 receptors(CD4)protein were detected by Western blot.Results The levels of IL-1 β in serum in the experimental-M,-H groups,model group and normal group were(82.15±13.66),(75.56±11.07),(118.20±19.31)and(23.47±4.72)pg·mL-1;serum IL-6 levels were(71.54±16.48),(58.57±15.62),(140.60±5.76)and(30.33±4.15)pg·mL-1;serum IL-10 levels were(48.64±5.60),(52.65±7.99),(27.10±4.91)and(61.90±10.44)pg·mL-1;serum TNF-α levels were(70.33±8.51),(66.55±8.12),(90.88±4.90)and(34.18±4.15)pg·mL-1;the relative expression levels of MHC Ⅱ protein were 0.34±0.04,0.15±0.06,0.08±0.05 and 0.53±0.59;the relative expression levels of CD4 protein were 0.79±0.08,0.92±0.12,0.99±0.11 and 0.54±0.14,respectively.Compared with the model group,the above indexes in the experimental-M,-H groups showed statistically significant differences(P<0.05,P<0.01).Conclusion Melezitose could effectively improve the symptoms of UC mice;the mechanism may be through down-regulating MHC Ⅱ protein and up-regulating CD4 protein to activate T cell signal pathway to play an anti-inflammatory effect.