Abstract: Objective To discusses pathogenesis of the acute hepatitis B by clinical analysis. Methods To summarize liver function injury index changes in 36 cases of the acute hepatitis B, and observe HBV-M, HBV DNA change files in the course of the acute hepatitis B. Results In the early stage of HBV infection, HBV DNA positive rate is 50%, in the middle and low level of replication; HBsAg has higher titre in the early stage, gradually decline, until the below detection limit. Anti-HBs titre increased with the duration extension. the change files HBeAg, anti-HBc and HBsAg are the same, but the time lagged behind HBsAg. Damages of liver function and HBV-M, HBV DNA replication levels are unrelated. Conclusions In the early stage of acute hepatitis B, HBV clear has occurred, etiological indicators below detection limit in a short time. Understand the change files of HBV-M and HBV DNA in the course of the acute hepatitis B, has important significance to diagnosis, treatment and prognosis of the acute hepatitis B.