Hepatitis B generally refers to chronic hepatitis B, which is caused by infection with the hepatitis B virus. The common causes of infection are mother-to-child transmission, blood transmission and sexual transmission. The most important transmission route for hepatitis B is mother-to-child transmission, which is responsible for about 30-50% of hepatitis B cases in China. Vertical transmission is mostly due to the newborn’s contact with the blood of the HBV-positive mother during delivery, and living closely with a mother who has HBV after birth is called horizontal transmission. Also, this condition then causes familial aggregation of hepatitis B. Blood transmission is common from medical sources and transfusions, where the input of blood or other blood products already infected with hepatitis B virus may cause hepatitis B infection after transfusion. At the same time, if medical equipment contaminated with HBV is used repeatedly without strict sterilization during hospital examination and treatment, there is a great chance of hepatitis B virus infection. It is common in some backward development areas where there is no awareness of hepatitis prevention. Sexual transmission is also the main transmission route of hepatitis B. Especially those who have multiple sexual partners have a significantly higher risk of HBV infection, and sharing razors and toothbrushes can also transmit hepatitis B virus. Hepatitis B is a very common infectious disease, it is important to look at the disease and those who have been infected with hepatitis B correctly, face it scientifically, and actively prevent and treat it.