Lung adenocarcinoma (AD) is a common variant of lung cancer.Programmed cell death 1 /Programmed cell death ligand 1(PD1/PD-L1) is a promising immunotherapy target which has achieved promising results in advanced NSCLC patients in the ongoing clinical trials,and PD-L1 expression may be an important biomarker of predicting clinical response.In this study,we will evaluate PD-L1 expression and analyze its expression with the clinic pathological characteristics and outcomes in 133 cases of resected lung adenocarcinoma.Protein expression of PD-L1 was examined by immunohistochemistry method using the VENTANA PD-L1 (SP263) rabbit monoclonal antibody.Messenger RNA level of PD-L1 was evaluated by in situ hybridization method.PD-L1 expression rate in lung AD is 16.5% at the mRNA level and 13.5% at the protein level,which the kappa coefficient of the two examination methods is 0.824 (P=0.219,highly correlated).PD-L1 expression in lung AD was found to highly expressed in male patients and smokers (P=0.019 and 0.002),while no association were identified between PD-L1 expression and age,tumor size,clinical stage,positive pleural invasion,lymph node metastasis or therapy methods.Overexpression of PD-L1 was a significant indicator of shorter recurrence free survival time and overall survival (P=0.000 and 0.000).Multivariate analysis revealed that PD-L1 expression was an independent risk factor for poor RFS and overall survival (P=0.009 and 0.016).PD-L1 overexpression is more frequently observed in male patients and smokers in lung adenocarcinoma.PD-L1 expression is an indicator of worse prognosis in surgically resected lung adenocarcinoma patients.