Abstract: OBJECTIVE To observe the effect of Cephalotaxus fortunei extract on T cell behavior and immunity of sepsis mice. METHODS Totally 40 SPF male BALB / c mice were enrolled in the study, 10 of which were assigned as the normal control group, and 30 were used to establish sepsis model and were divided into the model group, the positive control group and the Cephalotaxus extract group. The positive control group was treated with Xuebijing, the Cephalotaxus extract group was treated with cephalotaxine, the normal control group and the model group were given intraperitoneal injection of equal dose of normal saline. The proliferation and cycles of the T cells of the four groups of mice were detected, the pathological tissues of the mice were observed, and the tumor necrosis factor - α (TNF - α) level, content of cortisol, thymus index, phagocytic function of neutrophils (PMN) and leukocyte migration index of the mice were determined. RESULTS The levels of expression of CD₂₅, CD₆₉ and CD₇₁ of T cells, proliferation rate of T cells, TNF-α level and leukocyte migration inhibition index (MII) of the Cephalotaxus extract group were significantly lower than those of the positive control group; the content of cortisol, PMN phagocytosis rate and thymus index of the Cephalotaxus extract group were higher than those of the positive control group(P＜0.05). The levels of T cells in S and G2/M phase were significantly lower in the Cephalotaxus extract group than in the positive control group (P<0.05). CONCLUSION Cephalotaxus fortunei extract can inhibit the activation and proliferation of T cells and improve the immune function of the body by regulating the hypothalamus pituitary adrenocortical axis.