Abstract: Objective To study the dosimetric characteristics of helical tomotherapy（HT）,step and shoot intensity-modulated radiation therapy（SaS-IMRT） and 3-dimensional conformal radiation therapy（3D-CRT） for liver tumor and their difference in protecting high risk organs. Methods CT images of 16 patients with liver tumor who underwent radiation therapy in our department were selected.Target area and normal organs on each image were underlined by the same physician.HT,SaS-IMRT and 3D-CRT（five fields） were performed for each patient at the dose of 60Gy/20 fractions. Results The conformity index（CI） and homogeneity index（HI） in HT,SaS-IMRT and 3D-CRT groups were 0.796±0.076 and 1.044±0.019,0.663±0.108 and 1.059±0.164,0.540±0.075 and 1.077±0.010,respectively（P=0.005）.The average dose and V10-V50 of liver were lower in HT group than in SaS-IMRT and 3D-CRT groups（P=0.005）.The maximal and average doses for the right kidney and stomach,and the maximal dose for the spinal cord were lower in HT group than in SaS-IMRT and 3D-CRT groups,and in SaS-IMRT group than in 3D-CRT group（P=0.005）. Conclusion The volume,CI and HI covered by the prescribed dose for liver tumor radiotherapy are advantageous for HT group,followed by SaS-IMRT group and 3D-CRT group.