【Objective】To compare and contrast the dosimetry between Tomo planning and BrainLab planning for lung metasta? ses in stereotactic body radiation therapy（SBRT）.【Methods】Four Patients with one，two，three and four metastases were selected. The PTV is 2.89 ± 1.15 cm 3 . Two plannings with total dose of 50 Gy to cover 95% of PTV，5 Gy/Fraction and 10 fractions were designed using Tomo planning system and BrainLab planning system respectively. The DVH curves of spinal cord，both lungs and normal tissue were compared. The conformity index andhomogeneityindex were analyzed as well.【Results】The homogeneity index （HI）and conformity index（CI）of the targets in Tomo planning system were 1.0314 ± 0.0700 and 0.687 ± 0.075，respectively. In BrainLab planning system the HI and CI of the targets were 1.0764 ± 0.1241 and 0.571 ± 0.042，respectively. To HI the P value in T test was less than 0.01 and the HI was better in Tomo than BrainLab and so was CI. The dose to spinal cord was higher in BrainLab planning system than that in Tomo. The dose to nomal tissue and both lungs were not different in the two planning systems and V20 of lung is as small as 10%. 【Conclusions】For small volume lung metastases which longest diameter were less than 4 cm，the tomotherapy should be better choice.