Objective To evaluate the effect of CT guided permanent 125I seeds implant brachytherapy on early non-small cell lung cancer (NSCLC) that is not suitable for operation.Methods 18 patients with early stage of NSCLC (stage Ⅰ and Ⅱ) were treated with CT guided permanent seeds 125I implantation from December 2002 to December 2006.The prescribed dose (PD)was 110 Gy,the median activity of 125I seed source was 0.7 mCi.The chest CT detection was performed at 1,2,6 months and 1 year after treatment.The tumor size and the clinical effect were compared before and after treatment.Results The minimum PD in target tumor was (107.7±5.3)Gy,D90 was (113±3.7) Gy,and D9o was more than mPD.The chest CT showed that complete relief (CR) was achieved in 7 patients (38.9％),partial relief (PR) was in 9 patients (50％),stable disease (SD) was in 2 patients (11.1％),no progress disease (PD) was found.The effective rate (CR rate + PR rate) was 92.9％ (16 cases),and local control rate was 88.9％ (16 cases) within one year.During the follow-up to December 2011,the 1,3 and 5 years cumulatively survival rate was 94.4 ％ (17 cases),72.2％ (13 cases),66.7％ (12 cases),56.8％ (10 cases) respectively.Median survival time was 58 months.Conclusions CT-guided permanent 125I seeds implant brachtherapy is effective in the treatment of early non-small cell lung cancer that is not suitable for operation.