Objective To observe the acute toxicity and preliminary clinical efficacy of intensify modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC).And compare it with threedimensional conformal radiotherapy ( 3D-CRT ). Methods From May 2008 to May 2009, 51patients with nasopharyngeal carcinoma were treated by IMRT with 2.2Gy/fraction at gross tumor volume (GTV) to a total dose of 70.4-74.8Gy/32-34 fraction, 1.8Gy/fraction at the clinical treatment volume Ⅰ (CTV 1) to a total dose of 61.2-64.8Gy/34-36 fraction and 2.0Gy/fraction at the clinical treatment volume Ⅱ (CTV2) to a total dose of 50-54Gy/25-27 fraction: 59 patients with nasopharyngeal carcinoma were treated by 3D-CRT with 2.0Gy/fraction at gross tumor volume-nx (GTVnx) to a total dose of 70-78 Gy/35-39 fraction,2.0Gy/fraction at gross tumor volume-nd (GTVnd) to a total dose of 70Gy/35 fraction, 2.0Gy/fraction at the clinical treatment volume Ⅰ (CTV 1) to a total dose of 60-64Gy/30-32 fraction and 2.0Gy/fraction at the clinical treatment volume Ⅱ (CTV2) to a total dose of 50-54Gy/25-27 fraction. Using chemotherapy of DDP+5-Fu in depend on the stage, Results Dose volume histogram ( DVH ) showed a better dose distribution and protection for normal tissue in group of IMRT, especially parotid.Acute toxicity was well tolerated and no grade V side effects occurred in group of IMRT. The patients showed xerostomia by IMRT are less than the group by 3D-CRT. The difference between the two groups was obvious. 28 patients had complete response(90.3%) while 3 patients had partial response after completion of treatment, giving a 1-year survival rate of 100%. Conclusion IMRT yields better dose distribution and acceptable toxicity than the 3D-CRT in both early and advanced stage nasopharyngeal carcinoma. The preliminary clinical result is encouraging, but clinical efficacy and complications for long-term need to be further studied.