Objective To investigate the effects of metformin on the proliferation， migration and epithelial mesenchymal transition of gastric cancer cells.Methods Gastric cancer cells were treated with different concentrations of metformin (0，10， 20， 40 mmol/L). And the cells were divided into four groups: CN group and metformin treated group (10， 20， 40 mmol/L). Cck8 reagent was used to detect the proliferation activity of GC cells treated with different concentrations of metformin. Scratch test and Transwell test detect the influence of metformin on migration in GC cells. Western blot was used to detect changes in the expression level of EMT (epithelial-mesenchymal transition) related proteins in GC cells.Results Compared with the control group， the proliferation activity of the experimental group decreased significantly with the increase of concentration (F=22.65）.Compared with the control group， the migration rate of the experimental group decreased significantly with the increase of concentration (F=27.22， P=0.0003)， Western blot results showed that the expression of E-cadherin protein in experimental group was higher than that in control group， and vimentin protein expression was lower than that in control group (E-cadherin protein：F=64.82， P<0.0001；vimentin protein：F=11.28， P=0.003).Conclusion Metformin inhibits the ability of migration by inhibiting EMT in GC cells.