Abstract: Objective Hepatitis B virus （HBV） genotypes and pre-core mutations were studied in patients with HBV infection. Methods Viral DNA was extracted from serum samples of 740 patients with hepatitis B and liver cirrhosis from August 2010 to October 2011,and HBV genotypes and pre-core mutations were detected by ABI sequencing instrument. Results Among 740 patients with HBV infection,40（5.41%） were with HBV genotype B,695 （93.92%） were with genotype C,and 5 （0.68%） were with genotype D infection;377 （50.95%） patients carried mutations related to lamivudine,adefovir dipivoxil and entecavir resistance,among whom 195 patients （51.72%） has a definite history of application of nucleos（t）ide analog （NA）. Out of the 195 patients,there were 12 patients with HBV genotype B and 183 with genotype C infection. Also among these patients with definite NA history,118 patients were with CHB,and 77 patients were with liver cirrhosis,and the major resistant mutations were M204V+L180M,M204,M204I+L180M and A181V;Serum HBV DNA load was related to NA resistance（x²=0.496,P<0.001）,but not age,gender,disease severity （CHB or cirrhosis） and ALT levels;Besides,a number of new mutations,e.g. rt64,rt126,rt178,rt129 and so on were found in this series. Conclusions The administration of NA might results in mutation of hepatitis B virus and drug resistance,and the mutations have certain characteristics. Dynamic monitoring of serum HBV DNA load will help early detection of gene mutation and drug resistance.

Key words: Hepatitis B, Mutation, Nucleos（t）ide analog, Drug-resistant