As the firstline drug for the treatment of diabetes, metformin not only has the effect of reducing blood glucose, but also has biological effects of antitumor. Clinical epidemiological studies show that type 2 diebetes can increase the risk of pancreatic cancer. Therefore, metformin has received more and more attention on the treatment and prevention of pancreatic cancer. The epidemiological data reveals that metformin can reduce the incidence of pancreatic cancer of patients with diabetes, which might be a new strategy for the treatment of pancreatic cancers. This paper reviews the relationships between metformin and the treatment of pancreatic cancer in terms of epidemiology and molecular mechanisms involved.