Abstract: Objective To investigate the efficacy and side effect of pemetrexed plus Cisplatin on chemotherapy-naive patients with advanced nonsquamous non-small cell lung cancer. Methods Thirty-six chemotherapy- naive patients with advanced nonsquamous non-small cell lung cancer confirmed by histology or cytology were enrolled in this study.Chemotherapy regimen: patients were given pemetrexed 500 mg/m2on day 1 and cisplatin 75 mg/m2on day1 or 25mg/(m2·d)day 1～3 by intravenous infusion,every 21 days as one cycle.The patients received at least 2 cycles chemotherapy,but no more than 6 cycles.The efficacy and side effects were evaluated. Results Thirty-six cases received 154 cycles chemotherapy with 4.2 cycles on average.There was no case with complete response.Seventeen cases had partial response (PR),nine cases had stable disease(SD) and ten cases had progressive disease(PD).The responsive rate was（CR+PR）46.2%,and the disease control rate（CR+PR+SD）was 72.2%.The progression free survival（PFS）time was 4.6 months.The common side effects were grade Ⅰ～Ⅱ myelosuppression.There was no case with chemotherapy-related death. Conclusion Pemetrexed plus cisplatin has better efficacy in chemotherapy-naive patients with advanced nonsquamous non-small cell lung cancer,and the side effects were mild.