OBJECTIVE To explore the in vitro and in vivo inhibitory effects and mechanism of metformin on the malignant biological behavior of esophageal squamous cell carcinoma （ESCC） cells by the hypoxia inducible factor-1α （HIF-1α）/interleukin-8 （IL-8） signaling pathway. METHODS Human ESCC TE1 cells were assigned into blank group， metformin low-， medium-， and high-dose groups （0.5， 1， 2 mmol/L）， IDF-11774 （HIF-1α inhibitor） group （20 μmol/L）， and high-dose metformin+HIF-1α activator dimethyloxalylglycine （DMOG） group. After 24 h treatment， cell proliferation [measured by the positive rate of 5-ethynyl- 2′-deoxyuridine （EdU） and optical density at 450 nm （OD450 value）]， apoptosis， invasion and migration as well as mRNA expressions of proliferating cell nuclear antigen （PCNA）， Bcl-2 interacting mediator of cell death （Bim）， migration and invasion enhancer 1 （MIEN1）， and matrix metalloproteinase-9 （MMP-9）， and protein expressions of HIF-1α and IL-8 in the cells were detected. The xenograft tumor model of nude mice was established. Thirty nude mice were randomly divided into blank group， metformin low-， medium-， and high-dose groups （i.g. administration of metformin 62.5， 125， 250 mg/kg+i.p. administration of equal volume of normal saline）， IDF-11774 group （i.g. administration of 50 mg/kg IDF-11774+i.p. administration of equal volume of normal saline） and high-dose metformin+DMOG group （i.g. administration of metformin 250 mg/kg+i.p. administration of DMOG 250 mg/kg）， with 5 mice in each group. They were given relevant medicine， once a day， for 4 consecutive weeks； the mass and volume of the tumor and protein expressions of HIF-1α and IL-8 in the tumor tissue were determined. RESULTS The EdU positive rate， OD450 value， cell invasion number， scratch healing rate， mRNA expressions of PCNA， MIEN1 and MMP-9， protein expressions of HIF-1α and IL-8， as well as the mass and volume of transplanted tumors and protein expressions of HIF-1α and IL-8 in tumor tissues were decreased by metformin in concentration/dose-dependent manner （P＜0.05）. Additionally，metformin increased the apoptosis rate and mRNA expression of Bim in cells （P＜0.05）. The trend of changes in corresponding indicators in the IDF-11774 group was consistent with that in the metformin groups， whereas DMOG could significantly attenuate the aforementioned effects of high-concentration/high-dose metformin （P＜0.05）. CONCLUSIONS Metformin can inhibit the proliferation， invasion， migration of TE1 cells， and tumor growth of nude mice， and induce cell apoptosis， the mechanism of which may be related to the inhibition of HIF-1α/IL-8 signaling pathway.