Phyllanthus ussuriensis which belongs to Euphorbiaceae has been used as a component of Korean traditional remedy against hepatitis and jaundice. Aqueous methanolic extract of P. ussuriensis was tested for antiviral activity of hepatitis B virus (HBV) in HepG2 2.2.15 cells which were derived through transfection of cloned HBV DNA into HepG2 human hepatoblastoma cells. P. ussuriensis extract decreased the levels of extracellular HBV virion DNA and inhibited HBV replication at concentrations ranging from 50 to 500 ㎍/ml. Partitioning of water suspension of the extract revealed that the activity mainly resides in the EtOAc fraction. Consecutive purfication of the EtOAc fraction by silica-gel column chromatography resulted in the two active anti-HBV fractions. Southern blot analysis shows that the action mechanisms or active site of the two fractions seems to be different in terms of their inhibition of HBV replication steps.