Objective:To investigate the action of TNF-a,IL-6 and sIL-2R in the mechanism of ulcerative colitis.Methods:Bi-antibody radioimmune methods and ELISA methods were used to analysis the samples in TNF-a,IL-6 and sIL-2R of 25 cases with active ulcerative colitis.30 normal persons were assigned as the contrast group.The data of cytokines(TNF-a,IL-6,sIL-2R)among contrast group,the active and catabolic phases of ulcerative colitis were compared.That in catabolic phases of ulcerative colitis was also compared with that in contrast group,the difference were compared among slight,moderate and severe groups,The relativity among the serum level in TNF-a,IL-6 of active ulcerative colitis had been observed.Results:The level of serum TNF-a,IL-6 and sIL-2R in active ulcerative colitis was much more higher than catabolic ulcerative colitis and contrast group(P0.05).The level had no significant difference between catabolic ulcerative colitis and contrast group(P0.005).The level in severe group is higher than that in moderate and slight group(P0.05).Serum cytokines,TNF-a and IL-6 are positively related to active ulcerative colitis.(r=0.8476,P0.05).Conclusion:There is a severe disorders of cellular immunity in the patients with active ulcerative colitis.TNF-a,IL-6,sIL-2R etc play the very important roles in the genesis and development of ulcerative colitis.The serum level of the above cytokines not only reflected the development of ulcerative colitis but also could be used as biological index of the effect and estimate the prognosis.