Abstract: Objective This study was to investigate the relationship between Polymorphism missing or insertion in the 3′-untranslated region of thymidylate synthase gene and the sensitivity to the pemetrexed therapy for advanced lung adenocarcinoma. Methods The AollgTM probe combined with real-time fluorescence PCR technology was used to test 106 patients' with lung adenocarcinoma accepted pemetrexed therapy on their genotype TS of peripheral blood. We analyzed the patients carrying different genotypes of TS for the relationship between TS and chemotherapic sensitivity. Results (1)Among the 106 cases of patients with advanced lung adenocarcinoma， the frequency of polymorphism gene 6bp missing or insertion in the TS gene 3′-UTR 1494 bp were respectively: -6 bp/-6 bp 55.7%（59/106），-6 bp/+6 bp 44.3%（47/106），+6 bp/+6 bp 0%（0/106）. (2)The overall recent response rate was 23.58%. The chemotherapy on patients with -6 bp/-6 bp genotype was 4.382 times as effective as the ones with the -6 bp/+6 bp genotype ( 95% CI，1.462～13.130，P=0.008)；(3) The median PFS and the median OS difference had statistical significance between patients with the -6 bp /-6 bp genotype and those with the -6 bp / + 6 bp genotypes（3.400 months vs. 2.477 months，P=0.001；14.239 months vs. 12.194 months，P=0.000）， suggesting that the patients with the -6 bp /-6 bp genotypes had significant advantage in both OS， PFS. (4) Cox regression analysis showed the relation between patients' age and the pathologic stage: elder patients with -6 bp/+6 bp genotype were faced with higher risk of death. Conclusion 6 bp polymorphism gene' missing or insertion in the TS might influence the sensitivity to the pemetrexed therapy for advanced lung adenocarcinoma， which could be used as one of the prognositic genes for personalized treatment.