Abstract: To investigate the effect of Huangqin Tang on expression of cytokines and NF-κB p65 in rats with ulcerative colitis (UC), and to probe into its underlying mechanisms of action. The mode of UC rats with cell immunoreactivity was made using compound method (trinitrobenzene sulfonic acid and ethanol). Rats were randomly divided into control group, model group, SASP group and high dose, middle dose and low dose of Huangqin Tang group. The food intake, body weight and microscopic damage of rats in each group were evaluated after being treated for five days. The blood and colon tissue were also collected. Production of NO was detected by Griess assay, the expression levels of IL-6, TNF-α, PGE₂ were detected by ELISA. ICH method was undertaken to determine the expression of NF-κB p65 protein in colon tissue. The food intake and body weight of model group rats were lower than that of control group. The expression levels of NO, IL-6, TNF-α, PGE₂ in serum and NF-κB p65 protein of colon tissue in model group were higher than that of control group. The above indexes were ameliorated in high and middle dose of Huangqin Tang groups. But there was no significant difference with SASP group. NF-κB p65 may be involved in the pathogenesis of UC, and Huangqin Tang can inhibit the relative activity of NF-κB p65, and decrease the expression levels of NO, IL-6, TNF-α and PGE₂.