Abstract: Objective To compare the dose parameters, efficacy and adverse reaction of stage Ⅲ nonsmall cell lung cancer (NSCLC) patients treated with three-dimensional conformal radiotherapy (3D-CRT) in different periods. Methods Two hundred and three patients with stage Ⅲnon-small cell lung cancer (NSCLC) treated with 3D-CRT were divided into two groups, 72 patients treated from August 2000 to December 2004 (Group A) and the rest of 131 patients treated from October 2006 to December 2008 (Group B). Median and biological effective doses were 66 and 60 Gy for Group A and B, respectively. The dose parameters were evaluated by treatment planning system with software SPSS13.0. Results Dmax, Dmean and V65 of GTV, CTV and PTV of Group A were higher than those of Group B(P<0.05). GTVV50, CTVD95, CTVV60-50, PTVD100-90 and PTVV55-50 of Group B were higher than those of Group A(P<0.05). No signifi cant difference was found in GTVD100-90, GTVV60-55, CTVD90, CTVV60 and PTVV60 between two groups(P>0.05). The irradiated doses to lung, heart and spinal cord, and the occurrence rate of acute radiation induced pneumonitis and esophagitis in Group A were significantly higher than those in Group B(P<0.05). The 1-, 3-, 5-years and median overall survival (OS) were 54.6%, 18.8%, 14.5% and 14 months in the whole group. The corresponding survival rates of Group A were 54.6%, 18.8%, 14.5% and 14 months and those of Group B were 59.3%, 20.8, 16.9% and 18 months (χ²=4.409, P=0.036) respectively. There was no signifi cant OS difference between radiotherapy alone and combined chemo-radiotherapy (χ²=1.43, P=0.232). Conclusion With application of 3D-CRT got more mature, the dose distribution in stage Ⅲ NSCLC became more optimal.As planing dose and adverse reaction occurrence were decreased the actual tumor dose or clinical effi cacy was not sacrifi ced.