Objective To observe the effects of improving tumor cell hypoxia on radiotherapy in non-small cell lung cancer(NSCLC). Methods Forty-two patients with NSCLC on stage II to stage IV were enrolled randomly, of whom 38 patients were well documented. All patients were treated with oxygenator by intravenous oxygen delivery within thirty minutes before radiotherapy to increase partial pressure of blood oxygen and improve tumor cell hypoxia. The arterial blood gas was analysed for each patients before and after oxygen infusion. All patients receive radiotherapy at a dosage of 2 Gy each time per day, five times per week. The total dosage was 60 to 70 Gy. Another 37 NSCLC patients selected randomly in control group were treated by conventional radiotherapy. The therapeutic effects were analysed statistically according to WHO categorized standard. Results The mean PO2 was (85.6?7.5) mm Hg, (103?9.7) mm Hg, and SaO2 was (89.5?6.1) %, (94.4?5.2) % before and after oxygen infusion respectively in study group. The efficacy of radiotherapy was 63.16 %(24/38), which was higher than that in control group 43.24 % (16/37) (0.05