The invention discloses pharmaceutical application of N-methylcytisine to treatment of ulcerative colitis. An ulcerative colitis model is established to explore an ulcerative colitis protection effect of N-methylcytisine and a possible mechanism. According to experimental results, by application in a safe dose range, disease activity index, colon length and colon histopathologic changes can be remarkably improved by N-methylcytisine in dosage of 16mg/kg while inflammatory cell generation and NF-kB activation can be inhibited, so that the protection effect of N-methylcytisine is probably associated with an anti-inflammatory efficacy, and N-methylcytisine has a protection effect on ulcerative colitis.