A hepatitis B carrier is a person with chronic HBV infection who is infected with hepatitis B virus (HBV) and has been positive for hepatitis B surface antigen (HBsAg) for more than 6 months, but has no signs and symptoms of hepatitis and basically normal liver function. Hepatitis B virus carriers are one of the main sources of hepatitis B infection, and their infectiousness is proportional to the amount of hepatitis B virus DNA in body fluids. Hepatitis B virus carriers are divided into two categories: chronic hepatitis B virus carriers and inactive hepatitis B virus surface antigen carriers: 1, chronic hepatitis B virus carriers: the hepatitis B virus replication in these patients is more active, so they are highly infectious. 2, inactive hepatitis B virus surface antigen carriers: this type of patients, hepatitis B virus DNA is negative, so their infectiousness is small or non-infectious. But the patient can still have the hepatitis B virus in his body, only to stop replicating and no longer release the virus into the blood, which means that neither the virus nor the lesion is active. The main ways of transmission for hepatitis B virus carriers are mother-to-child transmission, blood and body fluid transmission, and sexual transmission. Therefore, carriers of hepatitis B virus are contagious, but the strength of their contagiousness may vary. To prevent infection it is advocated to take active or passive immunization, to strengthen blood management, to develop good personal hygiene habits, to cleanse oneself, etc.