Abstract: Obj ective To investigate the changes of cytokeratin 1 9 fragment (CYFRA211),carcinoembryonic antigen (CEA),sugar decomposition enolase (NSE),carbohy-drate antigen 125 (CA125),carbohydrate antigen 199 (CA199)in non-small cell lung cancer pa-tients before and after chemotherapy and explore its clinical significance.Methods A total of 60 pa-tients with advanced non-small cell lung cancer were treated with 2 cycles (3 weeks per cycle)of cis-platin plus gemcitabine chemotherapy (GP).Serum CYFRA211,CEA,NSE,CA125,CA199 in patients were detected before and after chemotherapy.Results Positive rates of CYFRA211, serumCEA ,NSE ,CA 1 2 5 and CA 1 9 9 before chemotherapy in all patients were 6 1 .6 7%,5 1 .6 7%, 71.67%,53.33%,31.67%.Positive rates of serum CEA,CA125 adenocarcinoma were signifi-cantly higher than patients with squamous cell carcinomas (P<0.05 or P<0.01 ).The positive rate of NSE staging for stage IV patients was significantly higher than that in stageⅢpatients (P<0.05).After chemotherapy,5 cases had complete response,14 cases had partial response,25 cases had stable disease (SD),16 cases had progressive disease (PD).Among them,the indexes of patients with CR,PR were significantly lower than those before treatment (P<0 .05 ),SD patients with serum NSE,CA125 levels were significantly lower (P<0.05),PD patients serum CYFRA211, CEA,CA125 levels significantly increased than before treatment (P<0.05 ).Conclusion Serum CYFRA211,CEA,NSE,CA125,CA199 level can reflect Chemotherapy curative effect for patients with advanced non-small cell lung cancer.The short-term effect,tumor stage,and serum CYFRA211 levels before chemotherapy are the independent factors of prognosis.