To study the effect of endostar on the expression of hypoxia-inducible factor 1 (HIF-1) and vascular endothelial growth factor (VEGF) and radiosensitization, the changes of A549 cells treated by endostar, radiotherapy and radiotherapy plus endostar were checked by flow cytometry (FCM), methyl thiazolyl tetrazolium (MTT), hoechst staining, and enzyme linked immunosorbent assay (ELISA). The results showed that endostar could block cell periods of A549 and stopped the cell cycle at G2/M and S periods. Cell growth inhibiting and apoptotic rate in the combination group were higher than those in other groups. Meanwhile, the levels of HIF-1 and VEGF expression in the combination group were lower than those of other groups. It suggested that endostar significantly sensitizes the function of radiation in A549 cells by arresting the cell cycle at stage of G2/M and S, increasing the cell growth inhibiting and the apoptotic rate, down-regulating the expression of HIF-1 and VEGF.