As a safe and effective antidiabetic drug, metformin has been considered to be the first line drug for the therapy of diabetes. With further research on metformin, it turns out that metformin can not only lower blood glucose but also display certain benefits for patients with polycystic ovary syndrome and nonalcoholic fatty liver disease, which is independent of the hypoglycemic effect of metformin. Furthermore, metformin can block cancer cells growth by activation of AMP-activated protein kinase and inhibition of mammalian target of rapamycin signaling pathway. In recent years, the effects of metformin on anti-atherosclerosis, endothelial function protection and other cardiovascular benefits have also become a research hotspot.