Objective To investigate the expression of hypoxia-inducible factor-1 alpha (HIF-1 α),vascular endothelial growth factor-A (VEGF-A) and vascular endothelial growth factor-D (VEGF-D)in hypoxic environment as well as the relationship between HIF-lα and VEGF-D.Methods Human esophageal cancer cell line EC9706 was cultured under hypoxia environment for 6,12 and 24 h,the cell radiosensitivity was evaluated by survival curve.HIF-1 α siRNA was constructed and transfected into human EC9706 cells.Protein expressions of HIF-1 α,VEGF-A and VEGF-D were analyzed by Western blot before and after RNA interference.Results EC9706 cells under hypoxia showed radioresistance with a SF2 of 0.62 higher than that of normoxic cells of 0.43.Moreover,the protein expressions of HIF-1α,VEGF-A and VEGF-D were all increased (F =205.24,227.88,130.55,P ＜0.05) due to hypoxia treatment.On the contrary,after HIF-1α siRNA transfer,the protein expressions of HIF-1α,VEGF-A and VEGF-D in EC9706 cells were not influenced by hypoxia treatment.Conclusions EC9706 cells in hypoxic environment was radioresistance,and the upexpressions of HIF1α,VEGF-A and VEGF-D may be involved.