Background: Hypoxia is known as an important trigger for the development and progression of human cancers. Heat shock proteins (Hsps) may be up-regulated in response to cellular stressors including hypoxia. To date, the functional role of Hsps within hypoxic tumor microenvironment for esophageal squamous cell cancer (ESCC) remains poorly defined. Methods: CoCl2 was used to induce hypoxia that mimics a hypoxic tumor microenvironment in cultured ESCC cells. Successful induction of hypoxia was confirmed by 2’,7’–dichlorofluorescein diacetate (DCFDA) assay by detection of cellular reactive oxygen species (ROS). 7-Dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), a selective Hsp90 inhibitor, was used to treat 2 ESCC cell lines, KYSE-170 and -510 cells pretreated with or without CoCl2, an agent to induce a hypoxic tumor microenvironment. Cytotoxicity (MTT) and migration assays were conducted in KYSE-17 and -510 ESCC cells in response to different concentrations of CoCl2, followed by protein expression of Hsp 90, vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1a (HIF-1a), mTOR as well as markers related epithelial-mesenchymal transition (EMT) such as snail or E-cadherin, by immunoblot or ELISA. In parallel, cell proliferation and migration assays of ESCC cells were analyzed. Results: CoCl2 induced hypoxia was supported by an induction of reactive oxygen species (ROS). CoCl2 (200 mM) significantly suppressed cell viability and proliferation with a concomitant up-regulation of VEGF and HIF-1a in a dose-dependent fashion. In contrast, cell migration was significantly increased in response to CoCl2, while down-regulating E-cadherin with concomitant increase in Snail expression. 17-DMAG decreased expression of VEGF and HIF-1a. In addition, it inhibited cell migration and invasion of ESCC cells were analyzed. Conclusions: Our data have shown that CoCl2 induced hypoxia promotes EMT and angiogenesis, which are inhibited by 17-DMAG, suggesting that hypoxia induced EMT and angiogenesis is Hsp 90 dependent in ESCC.