Abstract: Objective To explore the expression of peripheral blood CD4⁺CD45⁺T cells in patients with ulcerative colitis and its clinical value. Methods Eighty patients with UC in the First Affiliated Hospital of Liaoning Medical University from March 2012 to December 2013 were selected, with mildly active in 27 cases, moderately active in 28 cases and severe active in 25 cases. There were also 80 cases in healthy control group. The fl ow cytometry was used to detect the percentage of molecules in peripheral blood T cell surface CD4⁺CD45⁺of patients. And then the percentage of the content was compared to determine the level of severity of illness. Results The expression of CD4⁺CD45⁺T cells in peripheral blood was significantly higher than that of control group (52.93%±3.64% in UC group and 41.34%±2.94% in the control group, t=-22.159, P< 0.05). The expression of CD4⁺CD45⁺T cells in peripheral blood in mild activity period was 50.99%±1.45%, moderate activity period was 52.66%±1.41%, severe active stage was 55.18%±2.18%, which suggested that the moderate activity period was higher than the mild activity period, and the severe active stage was higher than the moderate activity period. Comparison between groups were statistically significant with F=39.850, P< 0.05. Conclusion The expression level of peripheral blood CD4⁺CD45⁺T cells in UC group is higher than that of control group. With the aggravation of disease, the peripheral blood CD4⁺CD45⁺T cells increases significantly, which has guiding sense of clinical diagnosis.