Abstract: Ketogenic diet is a diet type characterized by high fat, low carbohydrate, protein and other nutrients in an appropriate proportion. At present, ketogenic diet plays an important role in the treatment of intractable epilepsy. The latest research found that ketogenic diet can not only alleviate the symptoms of patients with Coronavirus Disease 2019, but also effectively control the blood glucose level and body mass of patients with obesity or diabetes. In the treatment of cancer, ketogenic diet can not only directly play a role in tumor inhibition, but also enhance the effect of other anti-cancer treatment. However, some studies had questioned the clinical effect of ketogenic diet, and proposed that long-term ketogenic diet may increase the incidence risks of tumors (such as colorectal cancer), cardiovascular diseases and metabolic abnormalities. This study reviewed the research progress of ketogenic diet in treating diseases in order to provide a new idea for objectively evaluating clinical value and optimizing the clinical application of ketogenic diet.