Abstract：Objective：To investigate the variation of the expression level of miR-155 and its correlation with proinflammation cytokines IL-2, IL-6 and INF-γ in plasma of the patients with depression. Methods：Real-time RT-PCR was used to determine the expression of miR-155 in plasma from 52 cases of depression patients before and after 8 weeks of antidepressant treatment. ELISA was used to measure the levels of IL-2, IL-6 and INF-γ in plasma, and 40 healthy individuals were used as normal controls. Results：The expression of miR-155 and levels of IL-2, IL-6 and INF-γ in plasma of depression patients before the treatment were significantly higher than those after treatment and control group (P<0.01). The expression of miR-155 was positively correlated with the levels of IL-2, IL-6 and INF-γ (r=0.753, 0.639 and 0.671 respectively, P<0.01). Conclusion：The expression of miR-155 in plasma of depression patients before treatment was significantly higher than that in the patients after treatment and healthy control, and correlated with the concentration of proinflammation cytokines, which indicated that miR-155 may play certain role in the mechanism of immunological imbalance of the patients with depression.