Objectlve:To investigate the expression characteristics of Livin and second mitochondrial activator of Caspase(Smac) proteins in non-small cell lung cancer(NSCLC),and analyze their effect on patients’prognosis.Methods:The expressions of Livin and Smac proteins were detected in 89 NSCLC tissue samples and 25 normal lung tissue samples by immunohistochemical technique.Results:The positive expression rates of Livin and Smac proteins in NSCLC tissues were 53.9%.and 58.4%respectively,higher than that in normal lung tissues(P＜0.01).Livin protein expression correlated with Smac protein significantly(χ2=18.451,P=0.000,r=0.455).The expression level of Livin protein was closely related to lymph node metastasis,TNM stage and histological type(P＜0.05),but not to sex,age,differentiation grade(P＞0.05).The expression level of Smac protein was closely related to lymph node metastasis,TNM stage(P＜0.01),but not to sex,age,histological types(P＞0.05).Kaplan-Meier analysis revealed a significant impact on survival by Livin protein in NSCLC (P＜0.01),but not by Smac protein(P＞0.05).Conclusion:Overexpression of Livin protein may play a promoting role in the occurrence and progression of NSCLC.Moreover,it may bring an adverse effect on patients’prognosis.Although overexpression of Smac protein affects the occurrence and progression of NSCLC,it has no relationship with the prognosis.Livin protein may be helpful to evaluate the progression of NSCLC,and to predict the prognosis.