Oxytocin plays an important role in the central nervous system. Oxytocin can not only control social behavior of people and animals, but also regulate appetite and fat metabolism through the Leptin induced signaling pathways. Oxytocin disorder can cause mental disorder and metabolic diseases. Oxytocin has been applied to treatment of mental illness, obesity and diabetes. Further studies on oxytocin may help to reveal the mechanisms of these diseases.