The aim of the study was to observe the variation of CD4(+)CD25(+) regulatory T cells in periphery blood and tumor microenvironment of non-small cell lung cancer (NSCLC) patients and the effects of CpG ODN. The proportion of CD4(+)CD25(+) regulatory T cells, Foxp3 gene expression, levels of tumor growth factor-β (TGF-β) and immunoreactive fibronectin-γ (IFN-γ) in the periphery blood of 30 NSCLC patients and 30 healthy volunteers were compared. These indicators were compared before and after CpG ODN treatment. Foxp3 gene expression in the tumor microenvironment of NSCLC patients was also observed. The results showed CD4(+)CD25(+) regulatory T cell proportion, Foxp3 expression and TGF-β levels in the periphery blood of NSCLC patients were higher than those of healthy volunteers (p < 0.05), and these indicators of patients were significantly decreased after CpG ODN 2006 treatment (p < 0.05). Foxp3 expression in the metastatic lymph nodes was higher than that in the non-metastatic ones of NSCLC patients (p = 0.000). In conclusion, a rise in the proportion of CD4(+)CD25(+)Foxp3(+) regulatory T cells was demonstrated in the periphery blood and tumor microenvironments of NSCLC patients. CpG ODN 2006 downregulated the CD4(+)CD25(+)Foxp3(+) regulatory T cells proportion and TGF-β levels in the periphery blood of these patients.