Fat is an important source of calories for the body and can be consumed in small amounts to produce high calories. The absorption of intestinal fat-soluble vitamins, cellular metabolism, and the body’s defense function are all dependent on the participation of fat. The essential fatty acids in fat are involved in the synthesis of phospholipids, which enable the smooth transport of fat out of the liver and are beneficial to the prevention of fatty liver. Fat also has the role of inhibiting the synthesis of fatty acids in the liver, and glycerol from fat decomposition can play a role in controlling obesity to a certain extent. Moreover, a diet high in monovalent unsaturated fatty acids does not have a greater effect on sugar and fat metabolism than a diet high in sugars, and a diet that restricts sugars but not fats can contribute to the regression of fatty deposits in the liver. For patients with fatty liver, the role of fat is equally important, and if fat intake is too strictly restricted, it is not only detrimental to the regression of liver fat, but even affects the normal physiological functions of the body. On the contrary, too much saturated fatty acids in the diet can increase free fatty acids in the blood, which can aggravate abnormal lipid metabolism and promote the progress of fatty liver, induce atherosclerosis and hypertension; too much intake of unsaturated fatty acids can cause gallstone disease and increase the chance of breast cancer and colon cancer. The high calorie content of fats and oils can cause weight gain if consumed in excess. In addition, if too much fat is consumed, the caloric intake of fatty liver patients treated with diet therapy will be significantly increased, which will break the reasonable ratio of nutrients and inevitably affect the intake of other nutrients, which is not conducive to the smooth implementation of diet therapy. Therefore, patients with fatty liver should have a moderate fat diet, which should be controlled within 20% of the total calories throughout the day, with unsaturated fatty acids as the main ingredients, such as soybean oil, corn oil, sesame oil and sunflower oil containing monounsaturated fatty acids, such as olive oil, canola oil and safflower oil containing polyunsaturated fats, which can supplement the essential amino acids needed by the human body, can lower plasma cholesterol, and can prevent Fatty liver induced by high-fat diet. Because regular consumption of saturated fatty acids such as lard, tallow, suet, butter, cream, coconut oil and palm oil can raise blood cholesterol levels, they should be strictly limited. It is important to make the normal ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids each in food fat reach (1U1U1) as much as possible for human health.