Objective To investigate the value of CT guided 125 I seed implantation combined with chemotherapy in the treat-ment of unresectable non-small cell lung cancer .Methods The related data of 42 cases of middle and advanced non-small cell lung cancer treated in this hospital from January 2012 to December 2016 were retrospectively analyzed .The group A (23 cases) received the 125I seed implantation combined with chemotherapy ,while the group B(19 cases) adopted the simple chemotherapy .All cases conducted the chest CT re-examination at 1 ,2 ,6 months after treatment .The curative effects and complications were compared be-tween the two groups .Results The total effect rate (RR) at 1 ,2 ,6 months had statistical difference between the two groups (P<0 .05) .The adverse reactions in the group A were small ,large amounts of pneumothorax (26 .1% ,6/23) ,bone marrow suppression (26 .1% ,6/23) ,nausea and vomiting(30 .4% ,7/23) ,which in the group B were d 5 .3% (1/19) in the group B were bone marrow suppression (36 .8% ,7/19) ,nausea and vomiting (26 .3% ,5/19) .No severe complications were observed .The occurrence rate of adverse reactions had no statistical difference between the two groups (P>0 .05) .The adverse reactions were improved after symp-tomatic treatment .Conclusion CT guided 125 I seed implantation combined with chemotherapy has higher effective rate and more significant effect in treating unresectable non-small cell lung cancer .