Fatty liver was rare in China in the past, and therefore little research was done to understand it. But in recent years, there is a rapid increase in the trend, and has become one of the important pre-cirrhotic lesions of liver fibrosis and cirrhosis. First, what is fatty liver normal people per 100 grams of liver wet weight contains about 4 to 5 grams of lipids, of which phospholipids accounted for more than 50%, triglycerides accounted for 20%, free fatty acids accounted for 20%, cholesterol about 7%, the rest is cholesteryl esters and so on. When the accumulation of lipids in hepatocytes exceeds 5% of the wet weight of the liver, or when more than 1/3 of the hepatocytes are histologically lipidic per unit area, it is called “fatty liver”. Depending on the amount of fat in the liver, fatty liver can be classified into three degrees: mild (5-10% fat), moderate (10-25% fat) and severe (almost all hepatocytes are steatotic). The fatty liver is also divided into three stages according to whether the liver tissue is accompanied by inflammation: stage I is “simple fatty liver” without inflammation; stage II is “steatohepatitis” with inflammation and fibrosis in the confluent area, and stage III is complete fibrosis with pseudobulbar formation. That is, “fatty liver cirrhosis”. Clinical diagnosis means 1.B ultrasound examination: diffuse fatty liver has its unique performance on ultrasound image, high echogenic spots, some people call it “bright liver”. Ultrasound can detect fatty liver with liver fat content of more than 30% and fatty liver with liver fat content of more than 50%, and the sensitivity of ultrasound diagnosis can reach 90%. CT: The CT value is significantly negatively correlated with the amount of liver fat deposition, and the ratio of liver/spleen CT value can be used as a reference standard to measure the degree of fatty liver because the CT value of the spleen is often fixed. CT is superior to ultrasound in the diagnosis of fatty liver, and its accuracy is better than that of ultrasound, but it is expensive and radioactive. 3.Magnetic resonance imaging (MRI): MRI and hepatic arteriography are mainly used for those who have difficulty in diagnosis by ultrasound and CT, especially when it is difficult to differentiate focal fatty liver from liver tumor. 4. The “gold standard” for the diagnosis of fatty liver is liver aspiration biopsy and histocytological examination. However, liver aspiration is not necessary for the diagnosis of obese people.