Objective To explore the effect of hepatitis B virus(HBV) on the expression of apolipoprotein B(ApoB) and its regulatory mechanism. Methods mRNA and protein expression of ApoB in HepG2 and HepG2.2.15 cells was measured by RT-PCR and Western blot, serum ApoB levels in patients with HBV infection and in healthy individuals were measured by biochemical analyzer Olympus 5400, the expression of ApoB difference among healthy individuals, patients with chronic hepatitis B, liver cirrhosis, and hepatocellular carcinoma were analyzed, HBV infectious clone pHBV1.3 was tranfected into HepG2 cells,and expression of ApoB and microsomal triglyceride transfer protein(MTP) was measured by RT-PCR and Western blot. Results Expression of ApoB mRNA and protein was lower in HepG2.2.15 cells than in HepG2 cells, serum apoB levels was much lower in patients with chronic hepatitis B and liver cirrhosis as compared to healthy individuals( P ＜0.05 ), HBV could inhibit the expression of ApoB and MTP at mRNA and protein levels. Conclusion HBV may downregulate the synthesis and secretion of ApoB via inhibits the expression of MTP.