Hepatitis B is a contagious and serious liver disease that can lead to liver inflammation and necrosis, liver fibrosis, cirrhosis and hepatocellular carcinoma. If not treated promptly and regularly, hepatitis B can seriously affect the life expectancy of patients. Hepatitis B virus (HBV) infection is a worldwide epidemic, with about 240 million people chronically infected with HBV worldwide, and about 650,000 people die each year from liver failure, cirrhosis and hepatocellular carcinoma caused by HBV infection. Hepatitis B is one of the common chronic infectious diseases in China, seriously endangering people’s health. There are about 93 million people with chronic HBV infection and about 20 million cases of slow hepatitis B. Among patients with cirrhosis and HCC, the proportion caused by HBV infection is 60% and 80%, respectively. Patients without cirrhosis are less likely to get primary hepatocellular liver cancer, but the annual incidence of liver cancer among patients with cirrhosis can be 3%-6%. Complications of cirrhosis in the decompensated stage include ruptured esophagogastric varices and bleeding, hepatic encephalopathy, ascites, hepatorenal syndrome, etc. Once ruptured esophageal varices and bleeding occur, the morbidity and mortality rate reaches about 20% within 6 weeks, and the 1-year morbidity and mortality rate is about 64%; the average survival period of hepatocellular carcinoma patients is about 6 months. This shows that liver failure, decompensated cirrhosis and hepatocellular carcinoma caused by hepatitis B are the key factors that determine the life expectancy of hepatitis B patients. It has been found that patients with hepatitis B who have sustained HBVDNA below 104 copies/mL or negative, normal ALT levels, and no or only mild inflammation in liver histology will have a much reduced risk of developing cirrhosis and hepatocellular carcinoma. Therefore, regular and effective antiviral treatment is the key measure to delay and reduce the occurrence of cirrhosis, hepatocellular carcinoma and their complications in patients with hepatitis B. As long as the hepatitis B virus in the patient’s body is suppressed, liver inflammation and necrosis will be improved, the disease will be controlled, and patients with hepatitis B can work and live normally, and their life expectancy is no different from that of healthy people. Therefore, hepatitis B is a serious liver disease that can lead to liver inflammation and necrosis, liver fibrosis, cirrhosis and hepatocellular carcinoma. Patients with hepatitis B should seek timely medical treatment and receive regular antiviral therapy to stop or delay the occurrence of serious complications in order to obtain the same life expectancy as that of healthy people.