Abstract： Objective To observe the therapeutic effect and toxicity of chemoradiation of locally advanced non-small cell lung cancer by intensity modulated irradiation combined with pemetrexed and cisplatin. Methods Fourty-two patients presented with Ⅲ - stage non-small cell lung cancer(Ⅲ、 25 patients, ⅢB 17 patients)received concurrent chemoradiotherapy. Intensity modulated irradiation technique was used to the total dose of 66 Gy and concurrent chemotherapy consisted of pemetrexed 500 mg/m2 on Day 1 and cisplatin 75 mg/m2 on Day 1 by intravenous infusion once every 3 weeks at the initiation of radiation.Patients received 4 cycles of chemotherapy. Results Thirty-four patients finished the whole of therapeutic schedule. And 2 patients received radiation with total dose of 54 Gy, 2 patients 56 Gy;3 patients received 2 cycles of chemotherapy, 1 patients 3 cycles of chemotherapy. Total effective rate was 79%. There were 2 patients with ≥3 grade marrow depression, 3 patients with 3 grade radiation esophagitis, 4 patients with ≥2 radiation pneumonitis, and 1 patient with 3 grade mucositis. The 1-year survival rate was 65%.Conclusion Recent effect was favourable and toxicity was tolerable for chemoradiation of locally advanced non-small cell lung cancer by intensity modulated irradiation combined with pemetrexed and cisplatin.