Abstract: Hepatits B virus (Hepatitis B Virus, HBV) is known as one of the smallest animal DNA viruses ,It can cause Hepatitis B,which is widely disseminated and seriously infectious diseases.At present, there are about 400 million people worldwide carrying HBV, in an average about one million people of the infected people will die from HBV-related liver cancer in a year. In China, about 50 million people die from the advanced liver cirrhosis and liver cancer caused by HBV infection.We summarize the characteristics , genome structure, variation and classification, replication model and transcription model,pathogenesis, detection of indicators of hepatitis B virus,.and intend to give some hints to the futher study of HBV.