【Abstract】 Objective To explore the dosimetric characteristics of two radiotherapy techniques, static Intensity Modulated Radio Therapy (sIMRT) and Helical Tomotherapy (HT), of simultaneous integrated boost of tumor bed after breast conserving surgery for left breast cancer. Methods Twenty three patients with tumor beds marked by silver clips after breast conserving surgery for left breast cancer were selected. Elekta Monaco 5.11 planning system was used to design sIMRT plan and Ankerui TomoTherapy planning system was used to design HT plan, with prescription dose PGTV: 5750cGy/25F, PTV: 5000cGy /25F. The dosimetric parameters of planned target areas and organs at risk between the two groups were compared. Results Conformity and uniformity of the HT plan for the target area is better than those of the sIMRT plan. The homogeneity index between the two is statistically different (P＜0.05), but the conformity index has no statistical difference (P=0.053, P=0.089). The organ-at-risk dosimetric parameters, left lung V5, V20, Dmean, right lung V5, Dmean, heart V30, Dmean, right breast Dmean, spinal cord D2, were compared, with the heart V30 of HT being lower than that of sIMRT (P＜0.05) and the other parameters of HT being significantly higher than those of sIMRT (P＜0.05). Conclusion Compared with sIMRT plan, HT plan had better conformity and uniformity of the target area, but sIMRT plan could protect the organs at risk better than HT plan. On the whole, sIMRT presented more benefits than HT plan in terms of simultaneous integrated boost of tumor bed after breastconserving surgery for left breast cancer.