Antimicrobial peptides (AMPs) comprise an important part of the innate immunity system of host organism and provide effective protection for the host against bacteria, fungi, protozoa and viruses. They are synthesized either by ribosomal or non-ribosomal peptide synthetase. Usually, AMPs are positively charged small molecular weight proteins and have both a hydrophobic and hydrophilic side that enables the molecule to enter the membrane lipid bilayer. In this review, recent discoveries on such physicochemical characteristics of AMPs as conformation, cationicity, hydrophobicity, amphipathicity etc.are discussed.