Fatty liver is characterized by excessive fat storage and steatosis in liver cells, which can be divided into non-alcoholic fatty liver and alcoholic fatty liver, with more causes, such as obesity, alcohol consumption, malnutrition, diabetes mellitus, and toxicity of some drugs. 1. Non-alcoholic fatty liver: mostly due to excessive fat deposition in liver cells caused by insulin resistance, common causes include obesity, type 2 diabetes mellitus, hyperlipidemia and so on, and poor lifestyle such as high-energy diet, sugar-sweetened beverages, and sedentary lifestyle also has certain influence on the development of the disease. 2. Alcoholic fatty liver: it is caused by the damage of alcohol to the liver, short-term large amount of alcohol or long-term intake of alcohol >40 g/day can increase the risk of disease, the metabolites of alcohol will directly damage liver cells, leading to hepatocellular steatosis, and with the progression of the disease can be developed into alcoholic hepatitis, alcoholic cirrhosis of the liver. There are many causes of fatty liver, and patients with fatty liver should seek medical advice in time to identify the specific causes under the guidance of professional physicians and intervene as early as possible to avoid delaying their condition.