To explore effects of Tetrastigma hemsleyanum Diels et Gilg flavone (THDEGF) on immune function and apoptosis-related proteins in tumor tissues of Lewis lung cancer mice.Sixty mice were randomly divided into control group,model group,high-dose,medial-dose and low-dose THDEGF group (100,50 and 25 mg/mL),10 cases in each group.They were continuously intervened for 14 days.After intervention,thymus index and spleen index in each group were detected.The apoptosis of transplanted tumor tissue was observed by HE staining and TUNEL staining.The expression of apoptosis-related protein was detected by Western blot.The ratio of regulatory T cells (Treg) in peripheral blood were detected by flow cytometer.The result showed that compared with model group,thymus index,spleen index and apoptosis rate of transplanted tumor tissues were significantly increased in high-dose THDEGF group and medial-dose THDEGF group (P<0.05),while expression of B-cell lymphoma/leukemia-2 (Bcl-2) was decreased (P<0.05),expression of Bcl2-associated X protein (Bax) and cleaved cysteine aspartase 3 (cleaved Caspase-3) were increased (P<0.05),proportion of CD4+CD25+Foxp3+ Treg cells was significantly decreased (P<0.05).With the increased dose of THDEGF,its effects were significantly enhanced (P<0.05).In conclusion,THDEGF can reduce the proportion of Treg cells in Lewis lung cancer mice,improve the cellular immune function,and induce the apoptosis of transplanted tumor tissues.