Purpose To investigate the association of the PD-1 and PD-L1 protein expression with K-RAS gene mutations in lung adenocarcinoma.Methods The protein expression of PD-1 and PD-L1 was detected by immunohistochemical EnVision two-step staining,the K-RAS mutation was examined by realtime fluorescent quantitative PCR.Results The positive rate of PD-1 and PD-L1 was higher in lung adenocarcinoma than benign lung disease (P ＜ 0.01).There was no relationship between PD-1 and PD-L1 protein expression with the gender,age,smoking condition,differentiation,lymph node metastasis and TNM stages (P ＞ 0.05).The K-RAS gene mutations were detectable in 8 patients (22.2％) among 36 lung adenocarcinoma,there was no association between K-RAS gene mutation with the gender,age,smoking condition,differentiation,lymph node metastasis and TNM stages (P ＞ 0.05).The correction analysis showed that there was no relationship between PD-1 and PD-L1 protein expression with K-RAS mutation (P ＞ 0.05).Conclusion The positive rate of PD-1 and PD-L1 is higher in lung adenocarcinoma than benign lung disease,but there is no relationship among PD-1 and PD-L1 protein expression with its clinal pathological characteristics and K-RAS mutation in lung adenocarcinoma.