Abstract: Objective To investigate the expression of KAI1，as a suppressor of metastasis，in the tissues of NSCLC and its relationship with the clinicopathological indexes. Methods The expressions of KAI1/ CD82 protein were detected with Western blot in 48 cases of NSCLC from patients with lung cancer and benign lung tissue of patients with benign lung disease undergoing surgery in our hospital.The RT-PCR method was also used to assess KAI1 mRNA in the same tissue samples,and the results were statistically analyzed. Results The positive rates of KAI1mRNA in NSCLC and benign lung tissues were 52%,90% respectively；the positive rates of KAI1/CD82 in NSCLC and benign lung tissues were 48%,85% respectively（P<0.01）. The expression level of KAI1mRNA and KAI1/CD82 protein in lung cancer were lower than those in benign lung tissue（P<0.01).The expression level of KAI1/CD82 were correlated with tumor stage,grade of tumor differentiation and metastasis status （P<0.05)，among which the metastasis status in particular（P<0.01）.The expression of KAI1/CD82 had relations with its mRNA(P<0.01). Conclusion The down-regulation of KAI1 may be correlated with carcinogenesis,development and metastasis in NSCLC.Its reduction may be mainly at transcriptional level，and it could be used as a marker for predicting the potential metastasis and prognosis of patients with NSCLC.