The proportion and changes of CD4+CD25high regulatory T cells (Trs) in peripheral blood of non-small cell lung cancer (NSCLC) patients were analyzed and their clinical significance explored. The peripheral blood was collected from 61 patients with NSCLC and 15 healthy controls. By using monoclonal antibodies, the blood samples were evaluated with the flow cytometry for lymphocyte subsets (CD3+, CD4+ and CD8+) and CD4+CD25high Tr cells. The results showed that the proportion of CD4+CD25high Tr cells in NSCLC group was significantly higher than in control group [(4.36±2.07) % vs (2.04±1.03) %, P＜0.01]. The proportion of CD4+CD25 high Tr cells in late stage was higher than that in early stage [stages Ⅰ + Ⅱ (2.26±0.6) %; stage Ⅲ (3.28±1.38) %; stage Ⅳ(6.06±4.08) %] (P＜0.05). Kaplan-Meier survival analysis revealed that the prognosis of the patients who had higher proportion of CD4+CD25high Tr cells in peripheral blood was worse (P=0.0026). In conclusion, the relative increase in CD4+CD25high Tr cells in peripheral blood may be related to immunosuppression and tumor progression in patients with NSCLC. This finding suggests that CD4+CD25+high Tr cells in peripheral blood of NSCLC may be positive for prognosis analysis. The use of depletion of the CD4+CD25high Tr cell therapy to treat NSCLC patients may be an effective strategy.