Once the symptoms of liver cancer appear, it is often at an advanced stage and the treatment effect is poor at that time. Therefore, for the early diagnosis of liver cancer and the detection of early cases among asymptomatic people, it is of practical significance to control the disease and death rate of liver cancer. The main way of early diagnosis of liver cancer is to conduct liver cancer screening. In the past, early stage liver cancer could be detected only occasionally during upper abdominal surgery. Since the 1970s, after China advocated liver cancer screening, many patients with early stage liver cancer were found. Some data reported that 83.6% of the cases found in liver cancer screening were clinical liver cancer (meaning liver cancer without symptoms and signs); 53% were “small liver cancer” (liver cancer with maximum diameter less than 5 cm); 58% were single cancer nodes; 58.6% were intact peri-cancerous envelope; and 97.7% were without portal vein or hepatic vein thrombosis. 97.7%. In contrast, 0%, 13.1%, 23%, 38.4% and 42.7% of the cases were clinically diagnosed after the onset of the above mentioned conditions, respectively. The difference between the two is very significant, which fully illustrates that liver cancer screening can indeed detect liver cancer cases at an early stage. The most direct effect of liver cancer screening is to increase the chance of surgical resection. Most of the cases detected by liver cancer screening are in early stage and the size of cancer is small, so they can often be locally resected. Since the amount of liver removed is small, even patients with some degree of hepatic steatosis can tolerate it more easily. Early stage hepatocellular carcinoma often has a more complete envelope and less chance of intrahepatic dissemination, therefore, the chance of surgical resection is significantly increased in cases detected by screening. As more cases can be surgically resected, the overall prognosis of liver cancer patients is significantly improved. According to the data from the Institute of Liver Cancer of Shanghai Medical University, the 5-year survival rate after radical surgical resection of small hepatocellular carcinoma less than 5 cm in diameter is 72.9%, and the 5-year survival rate after surgical resection of hepatocellular carcinoma less than 2 cm is 86.4%. Since more cases can be resected; therefore, the 5-year survival rate of census-detected cases is significantly higher than the 5-year survival rate of clinically diagnosed cases after the onset, which are 28.6% and 5.6%, respectively. The 5-year survival rate of liver cancer patients who were detected by screening and obtained radical resection was as high as 66.7%. The above information proves that screening is of great significance for the early diagnosis and early treatment of liver cancer. Alpha-fetoprotein (AFP) test and B-mode ultrasound are the main tools for early detection and early diagnosis of liver cancer. If AF7 combined with B-type ultrasound test is used for screening liver cancer, if both of them show positive results, i.e. AFP > 400 micrograms per liter, and B-ultrasound reveals clear substantial occupying lesions in the liver area, then basically liver cancer can be identified. If AFP is positive and no occupying lesion is found by ultrasound, or if substantial occupying lesion is found by ultrasound, CT examination or MRI should be performed.