Abstract: Objective: To explore the expressions of aldehyde dehydrogenase 1(ALDH1) of the marker of tumor stem cells and KAI1 of tumor metastasis suppressor gene in non-small cell lung cancer(NSCLC),and analyze its clinicopathological significance.Methods: The protein expressions of ALDH1 and KAI1 in 106 NSCLC specimens and 40 normal lung tissues were detected using immunohistochemical EliVision^TM plus.Results: The positive rates of ALDH1 and KAI1 protein in NSCLC tissues and control tissues were 60.4% & 37.7% and 10.0% & 90.0%,respectively,there was significant difference between the two groups(P<0.01).The differences of the positive expression rates of ALDH1 and KAI1 protein in different differentiation degrees,lymph node metastasis and TNM stage in NSCLC tissues were statistically significant(P<0.05 to P<0.01).Spearman analysis indicated that the expression of ALDH1 was negative correlation with the expression of KAI1 in NSCLC tissues(P<0.05).Conclusions: The abnormal expressions of ALDH1 and KAI1 may be involved in the development,invasion and metastasis of NSCLC.The combined detection of ALDH1 and KAI1 may be of significant value in early predicting the invasion and metastasis of NSCLC.