Hepatitis A and hepatitis B are both viral hepatitis, hepatitis A is caused by hepatitis A virus, hepatitis B is caused by hepatitis B virus, due to the different pathogenic viruses, their transmission routes and the resulting clinicopathological changes are different. Hepatitis A is an infectious disease with inflammatory lesions in the liver, which is transmitted mainly through the digestive tract and can be transmitted through food and water, especially in areas with poor sanitary conditions. Hepatitis A virus is a hepatophilic RNA virus, the virus mainly invades the liver, mainly manifested as acute hepatitis, is a self-limiting disease, treatment methods are mainly supportive treatment, supplemented by appropriate amount of drug therapy, the prognosis is better. Preventive measures are mainly to raise awareness, improve hygiene, and strengthen water protection. Hepatitis B is caused by hepatitis B virus infection, the main transmission channels are mother-to-child transmission, blood transmission and sexual transmission, the virus infection can cause inflammation, necrosis and fibrosis of liver cells, clinical manifestations of chronic hepatitis symptoms such as gastrointestinal manifestations, jaundice and pain in the liver area, with the progression of the disease may gradually develop into cirrhosis, liver cancer. The principle of treatment is to reduce the replication of HBV virus, but a complete cure is difficult. Preventive measures include managing the source of infection, cutting off the transmission route and protecting susceptible people. In summary, although hepatitis A and hepatitis B are both viral hepatitis, they differ in many aspects, but in common they are both infectious diseases, which need to be taken seriously and actively prevented and treated.