Abstract: Objective To discuss significance of carcinoembryonic antigen level changes be-fore and after the treatment of gefinitib in patients with non-small cell lung cancer(NSCLC). Methods 40 patients with advanced NSCLC in Ⅲ~Ⅳ period were enrolled and given routine local chemotherapy and gEfitinib,and the therapy was which until the patients were intolerant to it.All the patients were given carcinoembryonic antigen (CEA)test before and after treatment and were divided into high CEA group and low CEA group according to CEA level before treatment.Follow-up lasted until December 2013,adverse reactions and PFS in 2 groups were observed.Results Before treatment,the difference was not significant in CEA levels in control group and uncontrolled group (P >0.05).After treatment,CEA levels in 2 groups were obviously lower than the treat-ment before (P <0.01)and CEA level in control group was obviously lower than that in the uncon-trolled group(P <0.01).Occurrence rate of adverse reactions in high CEA group was higher than low CEA group but the difference were not significant (P >0.05).Survival rates of 9 and 12 months in high CEA group were markedly higher than that in thee low CEA group (P <0.05). Conclusion CEA level can be considered as a biochemical index of assessing prognosis of gefitinib in treatment of advanced NSCLC.