Purpose To investigate relationship between PD-L1 molecule expression and Treg infiltration in non-small cell lung cancer ( NSCLC) tissue and to explore their clinical significance. Methods Immunohistochemistry was used to detect the PD-L1 molecules expression and Treg infiltration of 78 NSCLC tissues. The relationship among PD-L1 expression, Treg infiltration and clinic-pathological parameters was analyzed in the patients. Results PD-L1 molecule was highly expressed in lung cancer tissues than adjacent tissues (52. 5% vs 6. 4%), and same to Foxp3 +Treg (18. 63 ± 16. 67)/HPF vs (2. 96 ± 2. 97)/HPF. There was close relationship between PD-L1 expression and Treg infiltration with lymph node metastasis and clinical stage of patients, but was no statistical correlation with patient’ s age, gender, histological type and degree of differentiation of the tumor cells. PD-L1 expression was significantly higher in advanced stage than that in early stage (70. 0% vs 41. 7%) and same to Treg infiltration (73. 3% vs 35. 4%). There were also signif-icantly higher infiltration with lymph node metastasis than that without metastasis. In addition, PD-L1 molecule expression and Foxp3 +Treg infiltration were positively correlated (rs =0. 611, F=78. 82, P=0. 023). Conclusion There was strong relationship among PD-L1 expression, Treg infiltration and disease progress in lung cancer patients, and they possibly participate in the progression and immune escape of lung cancer.