Liver is the most complex organ in the human body, the assessment of liver function can be divided into static test and dynamic test, static test is more common (such as bilirubin, coagulation factors, albumin and other biochemical tests), but only through the static test, can not reflect the changes in liver function in a timely manner, and its role is limited, the dynamic test has the advantage of real-time quantitative assessment of liver function, and only the combination of dynamic and static tests can comprehensively assess liver function. Only the combination of dynamic and static tests can comprehensively assess liver function. As early as 1956, experts found that the determination of indocyanine green clearance can better reflect the dynamic changes in liver function, and can assess the cell integrity, processing capacity and excretion function and other effective liver function. Indocyanine chlorine is a pigment, non-toxic, which is selectively taken up by hepatocytes after intravenous injection and then gradually excreted into bile. However, in the past, the operation of this test is complicated, and blood must be collected and tested punctually for many times after injection, and the operation is relatively time-consuming and invasive, coupled with the price and the supply of raw materials and other issues are not widely used in the domestic clinic. In recent years, a new device has been developed by Japan Photonics, which can be instantly detected through the nasal mucosa or finger, and thus the rate of liver clearance can be calculated. This method has the following advantages: ① non-invasive probe, except for intravenous injection without any venous puncture; in the bedside can be tested, the results can be obtained within 6-10 minutes; ② easy operation, the results and the operator has nothing to do with the need for a specific professional and technical personnel; ③ indocyanine green clearing is the most sensitive and earliest to appear to reflect the function of the liver and the visceral perfusion of the indicators; ④ real-time reflection of the patient’s liver function, dynamic observation of liver function changes; ⑤ fixed quantity of liver function; ⑤ the liver function of the liver function of the patients. Observe the changes of liver function; ⑤ Quantitatively detect the size of liver function potential. It is found that indocyanine chloride clearance is more sensitive than applying liver enzyme system to assess liver dysfunction, and it has a certain role in the selection of surgical operation and the determination of the timing of surgery, which is mainly applicable to cirrhosis, liver fibrosis, chronic hepatitis, occupational and drug toxic liver disease, and there have been researches at home and abroad used for the judgment of the prognosis of acute and chronic liver failure, the judgment of the early dysfunction after liver transplantation, etc., and it can be made as the basis of liver transplantation. It is worth noting that at least 2 hours of fasting is required before the test, and there is no history of iodine or alcohol allergy. ICG clearance is greatly affected by hepatic blood flow, so any factors affecting hepatic blood flow will have an impact on the test results. In addition, serum turbidity and celiac disease will produce colorimetric error, and patients with biliary obstruction are not suitable for this test. Yu Wanyou, ICU of Critical Hepatitis, Tianjin Second People’s Hospital, Tianjin, China