We aim to study the effect of NU7026 on the proliferation and radiosensitivity of HepG2 cells, and to provide experimental data and advanced evidence for exploring anticancer and radiation sensitizing new drugs. Western blot was used to detect expression level of DNA-PKcs in HepG2 cells and the activity of p-DNA-PKcs/S2056 inhibited by NU7026. The DNA damage was judged by the expression level of γ-H2AX. The micronucleus experiment was taken to observe chromosome damage; clonogenic assay was performed to determine the radiosensitizing effect of NU7026. The results show that DNA-PKcs is highly expressed in HepG2 cells, NU7026 reduce the expression of p-DNA-PKcs/S2056 micro nuclear test and γ-H2AX test shows NU7026 could effectively prolong the time of DNA repair after irradiation, and significantly reduce cloning efficiency of cells induced by radiation. It can be concluded that NU7026 can enhance the radiation sensitivity of HepG2 cells and its mechanism may be related to inhibition of DNA-PKcs activity.Cited