In recent years, much progross have made on the mechanism of tumor tumorigenesis and development. Research has showed the tumor cell expressed the inhibitory molecules and formed a suppression microenvironment to avoid the cytotoxicity from the effctor immune cells. In this circumstance, tumor cell was able propagate limitless. In this study, we investigated the frequency of inhibitory cell CD4(+)CD25(+) Treg cell, the mRNA expression in plasma and the serum concentration of TGF-beta in the 40 cases of non-small cell lung cancer patients and 40 health physical examination volunteers. As it expected, in the peripheral blood, the frequence of Treg cell, the FOXP3 mRNA in the cancer tissue cell and the serum TGF-beta in the NSCLC patients is significant higher than the health voluteer. In addition, Foxp3 expression was interfered in human lung cancer cell line A549, which were co-cultured with CD4(+) T cells, to investigate the effect of Foxp3 on the proliferation of lung cancer specific T cells. Compared with control group, A549 cells with reduced expression of Foxp3 significantly promoted the proliferation of CD4(+) T cells and resulted in a significantly low level of TGF-beta (P<0.05). In conclusion, the CD4(+) CD25(+) Foxp3(+) Treg cells and TGF-beta were significantly increased in NSCLC patients. Elevated expression of Foxp3 in lung cancer cells was involved in the inhibition of the proliferation of tumor-specific T cells.