Objective To analyze the difference of prescription dose between ICRU report 83 and Chinese recommendation in the nasopharyngeal carcinoma (NPC) for intensity modulated radiation therapy (IMRT).Methods Eighty-four NPC were treated using IMRT technology from Jan 1,2010 to Apr 1,2012.All dose volume histogram of the 84 IMRT plan were analyzed retrospectively.The target volumes of planning gross tumor volume of nasopharynx (PGTVnx) or planning clinical target volume and high risk lymphatic drainage (PCTV1) and doses of D100,D98,D95,D50,D2 and D0 were recorded.The mean,standard error,medial,range,coefficient of variation (CV) of PGTVnx,PCTV1,and D100,D98,D95,D50,D2and D0 were calculated,respectively.The homogeneity index (HI) and deviation between D95 and D50 of PGTVnx and PCTV1 were calculated,respectively.The differentiation of grouping results were analyzed with grouped t-test method.Results The HI of PGTVnx and PCTV1 were 0.118 ± 0.045 and 0.272 ± 0.037,respectively.It is the bigger target volume,the worse HI;and the advanced T stage,the worse HI.Either PGTVnx or PCTV1,D95 were less than D50.The average deviation was-5.15％ and-10.97％,and the actual difference value was (382± 180) cGy (P=0.000) and (741± 140) cGy (P=0.000).Conclusions D550,which is the recommendation prescription dose of PTV in ICRU report 83,could evaluate accurately the IMRT plan with combining D98 and D2· When D50 is used to instand of D95,the prescription dose of PGTVnx and PCTV1 should increase 5％ and 11％,respectively.