Abstract: To understand the mechanism of biological activity of melittin, the behaviors of melittin in aqueous environment and its interaction with a variety of phospholipid bilayer membranes were studied by coarse grained molecular dynamics method. Results show that the melittin molecules can form multimer both in the aqueous environment and in the phospholipid bilayer. In each multimer, the relative positions between the melittin monomers are constantly changing and voids with no specific shapes may form between monomers to create transient pores or transmembrane channels in the membrane. The electrostatic interactions between the N-terminal and C-terminal positively charged residues of melittin molecules and the negatively charged phospholipid heads of phospholipid membrane play a key role in the biological function of melittin.