Objective To investigate the influence of nucleic acid extraction by boiling the serum samples and purifing nucleic acid from serum on HBV DNA detection by PCR. Methods The DNA templates from 2 serum samples with different HBV DNA concentration and 3 serum samples with hemolysis and non hemolysis for PCR were prepared by two kinds of method, i.e. by boiling the serum to release HBV DNA from the virus particles and by purifing the nucleic acid from serum. Then,the difference of reproducibility and HBV DNA quantitative values by PCR using the templates prepared by the two nucleic acid extraction methods was compared.Results HBV DNA quantitative values by PCR using the templates purified from the two samples were more reproducible( CV : 0.2165 and 0.3262, respectively) than those using the templates prepared by boiling the serum ( CV : 0.0699 and 0.1092, respectively). Moreover, when the concentration of hemoglobin in serum samples was higher than 5.89 ?g/L, the HBV DNA quantitative values by PCR using the templates purified from the samples were about one hundred fold more than those using the templates prepared by boiling the serum ( P