Antimicrobial peptides are important agents that are made by the immune system in response to pathogens. This kind of immune response exists in all animal categories from prokaryotes to humans. Different types of antimicrobial peptides have been identified and isolated from various organisms from bacteria to humans. These peptides, along with antimicrobial effects, also contain other biological activities such as anticancer, spermicidal, anti-diabetic, growth stimulant, and etc. Therefore, these natural compounds can be considered as new therapeutic goals in different areas, especially for prevention of infectious disease.