Abstract: The present work aims to observe the therapeutic efficacy and the side effect of chemoradiotherapy of locally advanced non-squamous cell lung cancer in the old patients using conformal irradiation combined with pemetrexed. Methods: Since January 2009, 23 older patients with locally advanced non-squamous cell lung cancer treated by conformal irradiation combined with pemetrexed were enrolled in the current work. Prospective clinical analysis of the short-term effect, 1-year survival rate, and adverse reactions was conducted. Results: Various short-term curative effects occurred in the patients after the treatment, that was, complete response in 2 of the 23 patients, partial remission in 15, and steady disease in 6. No progression of disease was found. Local recurrence occurred in 5 of the 23 patients. The rate of local control was 73%. One-year survival rate was 67% in these patients, among them the 1-year survival rate of stage IIIA patients was 82% and that of the stage IIIB patients was 63%. Therapeutic toxicity was tolerated, in which class I reaction ranked the first among adverse reactions, and class II reaction was noted only in a few cases. Conclusion: Short-term effect is favorable and toxicity is tolerable in chemoradiotherapy of locally advanced non-squamous cell lung cancer in older patients who underwent conformal irradiation combined with pemetrexed.