Abstract: Objective 　To investigate the expression of HIF-1 and vascular endothelial growth factor (VEGF) in human esophageal squamous cell carcinoma cell line EC9706 under hypoxia. To observe the effect of HIF-1αon hypoxia2activatad angiogenesis regulation pathway in esophageal squamous cellcarcinoma. Methods 　CoCl₂ was used as a chemical hypoxiainducible reagent to mimic tumor hypoxic microenviroment . mRNA and protein levels of HIF-1α and VEGF were detected by semiquantitative reverse transceiption-polymerase chain reaction ( RT-PCR) and immunohistochemistry. With RNA interference (RNAi) originated by small interference RNA ( siRNA ) to use siRNA transfected EC9706 cells. Western-blot was used to detect gene scilencing effect on HIF-1α. RT-PCR and immunohistochemistry were used to observe the change of VEGF gene expression af ter HIF-1αgene silence. Results 　Under hypoxia, mRNA level of HIF-1α was stable, while its protein level increased obviously. Both mRNA and protein levels of VEGF were up-regulated. The siRNA targeting HIF-1α gene down-regulated HIF-1 gene in EC9706 cells efficiently, and VEGF gene was down-regulated as well. Conclusion 　Hypoxia can increase protein level of HIF-1αin esophagus. HIF-1α up-regulates the gene expression of VEGF which promotes angiogenesis in esophagus under hypoxic microenviroment .