Surface antigen preS of Hepatitis B virus plays fundamental roles in mediating receptor recognition and virus internalization. Myristoylation at N-terminal Gly(2) residue of preS is essential for viral attachment and infectivity. A number of myristoylated proteins have been shown to undergo a conformational change (myristoyl switch) that alters their affinity to cell membrane. However, there is little knowledge about what effect this fatty acylation contributes in virus-host cell interaction. Here we demonstrated a new method for lipid modification of recombinant preS protein at N-terminal residue 2 with alkylating chemicals. Modified preS was able to inhibit HBV penetrating into HepG2 cells with an increased efficiency compared to unmodified form. Flow cytometric analysis indicated that lipid modification enhanced the binding affinity of preS to hepatocytes, but not resulting from hydrophobic interaction. CD analysis further revealed a conformational change of modified preS in the presence of membrane mimetics. These findings imply that the conformation transition induced by fatty acylation is important for efficient attachment of virus to cell receptors, and this method of chemical lipid modification provides a basis for designing therapeutic inhibitors to Hepatitis B virus.