With the regular application of two properly selected and tolerated antiepileptic drugs (single or combination) in patients with epilepsy, nearly 1/3 of patients still do not have complete seizure control, with consequences for cognition, memory, quality of life, psychosocial and growth and development of children. The ketogenic diet is a special dietary regimen with a long history; in 1911, French medical doctors discovered that a low-calorie vegetarian diet with periodic fasting helped control seizures. Although its anti-epileptic mechanism is still unclear, its effectiveness and safety are well established. Under normal circumstances, the energy needed to supply the human body for growth and life mainly comes from the three major nutrients of carbohydrate, protein and fat in food, with carbohydrate accounting for the largest proportion, about 65% of the total energy, and fat + protein accounting for 35%. Ketogenic diet is to change the proportion of the three major nutrients, emphasizing a diet high in fat, low in carbohydrates and appropriate protein, so that the body’s energy supply is converted to fat-based. In general, the classical ketogenic diet consists of long-chain triglycerides with a moderate amount of protein and a small amount of carbohydrate, with a “fat”: “protein+carbohydrate” ratio of 4:1. The ketogenic diet is difficult to adhere to at first because of the special food ratio configuration. The ketogenic diet is difficult to adhere to at first due to the special food ratio configuration, but is well tolerated by patients if the seizures are controlled.