Abstract: Objective To explore the effect of hepatitis B virus(HBV) on the expression of apolipoprotein A1 (ApoA1) and its regulatory mechanism.Methods RT-PCR and Western blot were used to measure the expression of ApoA1 in HepG2 and HepG2.2.15 cells,serum ApoA1 and high density lipoprotein cholesterol(HDL-C) levels in patients with HBV infection and in healthy individuals were measured by biochemical analyzer,statistical difference was analyzed by SPSS13.0,HepG2 cells was co-transfected with ApoA1 promoter containing the luciferase gene and HBV infectious clone pHBV1.3,luciferase activity was measured,expression of ApoA1 in HepG2 cells was measured by RT-PCR and Western blot after transfected with pHBV1.3.Results Expression of ApoA1 mRNA and protein was lower in HepG2.2.15 cells than in HepG2 cells,serum ApoA1 and HDL-C levels were much lower in HBV patients as compared to healthy individuals( P<0.05 ),HBV represses ApoA1 gene promoter activity,ApoA1 mRNA and protein expression in HepG2 cells.Conclusion HBV can inhibit the expression of ApoA1 bothin vivo and in vitro.