Objective To understand the hepatitis B virus(HBV)genotyping and pre-existing antiviral resistance mutation in the patients with clinical chronic HBV infection in Shenzhen area.Methods Serum samples in 244 cases of chronic HBV infection were detected for HBV genotyping and pre-existing antiviral resistance mutation by using PCR combined with reverse dot hybridization. Results In 244 cases of chronic HBV infection,3 kinds of genotype were found,including 143 cases(58.6%)of genotype B,100 ca-ses(41%)of genotype C and 1 case(0.4%)of genotype D;38 cases(15.57%)of pre-existing antiviral resistance mutation were de-tected out.The total detection rate of pre-existing antiviral resistance mutation was 15.57%,in which 22 cases(9.01%)were related with lamivudine resistance and 16 cases(6.56%)were related with adefovir dipivoxil resistance.Conclusion The genotype B and C are the main genotypes in Shenzhen area,and the incidence rate of pre-existing antiviral resistance mutation in the patients with chronic HBV infection is relatively high.The detection of genotyping and pre-existing antiviral resistance mutation of HBV has the important significance to predict the disease progression and guide the individulized treatment.