Objective:To develop a method for amplifying full-length DNA of hepatitis B virus(HBV) from serum samples and construct the complete genome clone of HBV. Methods:The full-length HBV DNA was amplified with long-PCR,the amplified product was identified by sequencing and cloned into pucl9 vector to construct a recombinant plasmid containing the complete genome of HBV,and then the X gene of HBV was amplified from the recombinant plasmid and sequenced. Results:The complete genome clone of HBV was acquired after determination by enzyme digestion and sequence ana1ysis,and the X gene can be amplified from the cloned HBV genome. Conclusion:The complete genome DNA of HBV can be amplified directly from serum samples,which provide the research basis for studying the relations between HBV genome mutation and its pathogenicity and the host anti-infection immune in whole level.