Antimicrobial peptides (AMPs) have recently gained much attention because of their ability to overcome drug resistance and have emerged as a potential new class of antibacterial agents. These peptides are part of the innate immune system of all living organisms, including vertebrates, insects, bacteria and plants. AMPs encompass a number of different classes, including those that are rich in a particular amino acid. Important subsets are peptides rich in Arg and Trp residues that have broad and potent antimicrobial activity. These residues possess some crucial chemical properties that make them important components of antimicrobial peptides. Trp side chains are also implicated in peptide and protein folding in aqueous solution, where they contribute by maintaining native and nonnative hydrophobic contacts. This has been observed for the antimicrobial peptide from human lactoferrin, possibly restraining the peptide structure in a suitable conformation to interact with the bacterial membrane. These unique properties make the Arg- and Trp-rich antimicrobial peptides highly active even at very short peptide lengths. The long peptides interact very weakly with the lipids membrane. The antivirus mechanism of the biologically active peptides (peptaibols) sheds light on the potential use of peptaibols in plant viral disease control. The serious problems caused by drug resistant bacteria have created an urgent need for the development of alternative therapeutics. In this respect, AMPs are considered as promising antimicrobial agents for producing new generation Antibiotics and also for improving plant resistance against bacterial and virus lesion. So it is reasonable to focus on small peptides.