This kit is used for qualitative determination of hepatitis B virus core antibody (HBcAb) in human serum or plasma. HBcAb is a kind of immunoglobulin which the virus stimulates the production of hepatocytes. The appearance of HBcAb positive indicates that the replication of hepatitis B virus in the liver is active, the hepatocytes are seriously damaged, and the infection is strong. When the body is infected with hepatitis B virus (HBV), the anti HBC will be positive in the early stage after the positive transformation of HBsAg in the serum. It is the early marker of HBV infection, which has existed for a long time in the serum. The high titer of anti HBC indicates the continuous replication of HBV in the body, and the low titer of anti HBC indicates the previous infection of HBV. It can not be used as the only index for the evaluation of patients' condition. It needs to be combined with the clinical manifestations of patients and other laboratory tests for comprehensive analysis of the condition.