Nowadays，diabetes mellitus and bladder cancer are major public health problems in the world，which have a great impact on human health. Additionally，there are more and more patients with diabetes mellitus complicated with different cancers. A large number of studies have shown that there are some connections between bladder cancer and diabetes mellitus. Diabetes mellitus not only has many common risk factors with bladder cancer，but also may increase the incidence of bladder cancer and have a certain impact on its prognosis. Without doubt，there have been some studies holding different views. In addition，some antidiabetic drugs has certain correlation with bladder cancer. This article reviewed the relationship among diabetes mellitus，hypoglycemic drugs and bladder cancer，as well as the effect of diabetes mellitus on prognosis of bladder cancer.