Objective：To investigate the postoperative expression of ribonucleotide reductase subunit M1（RRM1） protein in non-small cell lung cancer（NSCLC） at stage of Ⅱ b/Ⅲ and to discuss the effect of RRM1 protein expression on disease free survival（DFS） of patients underwent adjuvant chemotherapy. Methods：Totally 100 patients with NSCLC at stage of Ⅱb/Ⅲa who underwent radical surgery were included in this study. The expression of RRM1 protein in tumor specimens was assayed by streptavidin-perosidase（SP）immunohistochemistry retrospectively. Correlations between the expression of RRM1 protein and the clinical features or DFS time af－ter operation were analyzed. SPSS 13.0 was used to analyze the effect of RRM1 protein expression on the patients’ prognosis. Results：（1）No difference in the expression of RRM1 protein was found among patients with different genders，ages，smoking habits，patho－logical differentiation and stages（P＞0.05）. RRM1 protein expression was increased in squamous carcinoma than in non-squamous car－cinoma although there was no significant difference（44.1% vs. 30.3%，P=0.172）；（2）Patients with lower RRM1 protein expression ex－perienced longer DFS time compared with those with higher RRM1 protein expression（median DFS，14 months vs. 8 months，P=0.019 4）；（3）In patients with adjuvant chemotherapy of Gemcitabine/Cisplatin，squamous carcinoma led to longer DFS time than non squamous carcinoma（median DFS，14 months vs. 11 months，P=0.011 9）；lower RRM1 protein expression led to longer DFS time than higher RRM1 protein expression（median DFS，13 months vs. 6 months，P=0.021 7）. No difference in the length of DFS time was found in the patients with only surgery（median DFS，15.5 months vs. 13 months，P >0.05）. （4）COX multivariate regression analysis showed that the expression of RRM1 protein and pathological type were the independent prognostic factors of DFS in NSCLC at stage of Ⅱb/Ⅲa. Conclusion：RRM1 protein is a valuable predictive factor for Gemcitabine/Cisplatin adjuvant chemotherapy in NSCLC at stage of Ⅱb/Ⅲa.